Causes of acute undifferentiated fever and the utility of biomarkers in Chiangrai, northern Thailand

The challenges and potential solutions of achieving meaningful consent amongst research participants in northern Thailand: a qualitative study

BACKGROUND

Achieving meaningful consent can be challenging, particularly in contexts of diminished literacy, yet is a vital part of participant protection in global health research.

METHOD

We explored the challenges and potential solutions of achieving meaningful consent through a qualitative study in a predominantly hill tribe ethnic minority population in northern Thailand, a culturally distinctive population with low literacy. Semi-structured interviews were conducted with 37 respondents who had participated in scrub typhus clinical research, their family members, researchers and other key informants. A thematic analysis was conducted.

RESULTS

Our analysis identified four interrelated themes surrounding participants' ability to give consent: varying degrees of research understanding, limitations of using informal translators, issues impacting decisions to join research, and voluntariness of consent. Suggestions for achieving more meaningful consent included the use of formal translators and community engagement with research populations.

CONCLUSIONS

Participant's agency in decision making to join research should be supported, but research information needs to be communicated to potential participants in a way that they can understand. We found that improved understanding about the study and its potential benefits and harms goes beyond literacy or translation and requires attention to social and cultural factors.

A systematic review of neglected tropical diseases (NTDs) in Myanmar

BACKGROUND

Neglected tropical diseases (NTDs) affect most impoverished communities in developing countries, like Myanmar in Southeast Asia. NTDs have been understudied and underreported in Myanmar.

METHODS

A systematic review of published and grey literature (1900-2023) on neglected tropical diseases (NTDs) in Myanmar was conducted. The literature search included five international databases: PubMed, EMBASE, Ovid Global Health, and Web of Science Core Collection and one national database: the Myanmar Central Biomedical Library (locally published papers and grey literature). The selection criteria included articles with all types of study designs of current or previous infections conducted in humans, that reported NTDs, recognised by WHO, US CDC, and listed in PLoS NTDs. We included melioidosis and rickettsioses which we consider also meet the definition of an NTD.

RESULTS

A total of 5941 records were retrieved and screened, of which, 672 (11%) met the selection criteria and were included in this review. Of the included articles, 449 (65%) were published after 2000 and 369 (55%) were from two regions (Yangon and Mandalay) of Myanmar. Of the included articles, 238 (35%) reported bacterial NTDs, 212 (32%) viral NTDs, 153 (23%) helminth NTDs, 25 (4%) protozoal NTDs and 39 (6%) reported more than one aetiology. Based on reported frequency in descending order, the bacterial NTDs were leprosy, Escherichia coli enteritis, salmonellosis, cholera, shigellosis, melioidosis, leptospirosis and rickettsioses; the viral NTDs were dengue, chikungunya and Japanese encephalitis virus (JEV) infection; the protozoal NTDs were amoebiasis, giardiasis and leishmaniasis, and the helminth NTDs were ascariasis, trichuriasis, hookworm disease, filariasis and strongyloidiasis.

CONCLUSION

This review summarises NTDs reported in Myanmar over the past 100 years. The findings suggest that most NTDs are likely to be under reported, especially from the majority of the country which is far from academic centres. Research capacity building together with strengthening of laboratory systems would lead to better understanding of the true burden of NTDs in Myanmar.

TRIAL REGISTRATION

PROSPERO registration ID: CRD42018092627.

Community-level incidence and treatment seeking during febrile illness: Insights from health behaviour surveys in rural Thailand and Laos

OBJECTIVE

Critical gaps remain in understanding community perceptions and treatment-seeking behaviours in case of fever. This is especially relevant considering global antimicrobial resistance, where fever is assumed to provoke non-judicious antibiotic use. Our study objective was therefore to document the community-level incidence of fever, the resulting treatment-seeking processes, and their underlying behavioural drivers.

METHODS

In a cross-sectional observational design, we used descriptive and inferential statistics and multivariable regression analysis to estimate the population-level incidence of fever and individual and socio-economic factors associated with treatment-seeking process characteristics. We utilised a detailed publicly available survey of community-level treatment-seeking behaviour (collected in 2017/2018), comprising a representative sample of 2130 rural adults in Thailand (Chiang Rai Province) and Lao PDR (Salavan Province).

RESULTS

Fever was reported by 7.1% of the rural adult population in Chiang Rai (95% CI: 5.1%-9.0%) and 7.5% in Salavan (95% CI: 4.5%-10.5%) during a 2-month recall period. Treatment-seeking patterns varied by socio-economic characteristics like precarious employment. 69.3% (95% CI: 60.8%-77.7%) of fever episodes involved access to formal (public/private) healthcare providers, 11.0% (95% CI: 4.5%-17.5%) involved informal providers, and 24.3% (95% CI: 16.6%-32.1%) took place without either formal or informal healthcare access. Febrile patients had on average 0.39 antibiotic use episodes when accessing formal healthcare settings, compared to 0.05 otherwise (p < 0.01).

CONCLUSION

Treatment-seeking behaviour during fever varies according to population characteristics. Clinical studies would benefit from contextualising quantitative outcomes. Treatment algorithms for non-malarial febrile illnesses should involve outreach to informal healthcare and community settings to support patients in precarious circumstances, and antibiotic resistance interventions should prioritise formal healthcare facilities.

C-reactive protein and procalcitonin use in adults in low- and middle-income countries: a narrative review

Objectives

C-reactive protein (CRP) and procalcitonin (PCT) are widely used biomarkers in high-income countries. However, evidence for their use in low- and middle-income countries (LMICs) is scant. Because many factors, including rates of endemic disease, comorbidities and genetics, may influence biomarkers' behaviour, we aimed to review available evidence generated in LMICs.

Methods

We searched the PubMed database for relevant studies within the last 20 years that originated in regions of interest (Africa, Latin America, Middle East, South Asia or South East Asia), and full-text articles involving diagnosis, prognostication and evaluation of therapeutic response with CRP and/or PCT in adults (n = 88) were reviewed and categorized in 12 predefined focus areas.

Results

Overall, results were highly heterogeneous, at times conflicting, and often lacking clinically useful cut-off values. However, most studies demonstrated higher levels of CRP/PCT in patients with bacterial versus other infections. HIV and TB patients had consistently higher levels of CRP/PCT versus controls. In addition, higher CRP/PCT levels at baseline and follow-up in HIV, TB, sepsis and respiratory tract infections were associated with poorer prognosis.

Conclusions

Evidence generated from LMIC cohorts suggests that CRP and PCT may have potential to become effective clinical guiding tools particularly in respiratory tract infections, sepsis and HIV/TB. However, more studies are needed to define potential scenarios for use and cost-effectiveness. Consensus across stakeholders regarding target conditions, laboratory standards and cut-off values would support the quality and applicability of future evidence.

Aetiology of Acute Undifferentiated Fever Among Children Under the Age of Five in Vietnam: A Prospective Study

BACKGROUND

To investigate the aetiology of acute undifferentiated fever (AUF) among children under the age of five in Vietnam.

METHODS

This prospective study was conducted in the Thai Binh paediatric hospital, between July 2020 and July 2021 among children with AUF at admission. Real-time PCR testing 18 microbial pathogens were done on blood samples.

RESULTS

286 children were included, with median age of 16 months. 64.7% were male. 53.9% were positive for at least one pathogen by PCR. Enterovirus, human herpesvirus 6, adenovirus, and varicella zoster virus PCR were positive for 31.1, 12.6, 1.4, and 1.0% patients, respectively. Other pathogens tested negative by PCR. During the hospital stay, based on clinical criteria 47.2% children secondarily presented with signs of respiratory tract infections, 18.9% had hand, foot and mouth disease, 4.6% had chickenpox. 4.2% presented signs of central nervous system infections, 1.0% had dengue (antigenic test) and 1.0% had signs of gastrointestinal infection. Finally, 23.1% patients presented a fever with or without a rash and no other symptoms and ultimately received a diagnosis of AUF.

CONCLUSION

Real-time PCR of blood is useful for detecting pathogens and diagnosing infectious causes of AUF. Further prospective studies with blood and urine culture testing and PCR investigation of not only blood but also cerebrospinal fluid, throat, and skin samples according to symptoms would be of interest to confirm the predominance of viral infections in children with AUF and to guide therapeutic options.

Vulnerability and agency in research participants' daily lives and the research encounter: A qualitative case study of participants taking part in scrub typhus research in northern Thailand

BACKGROUND

Researchers have a responsibility to protect all participants, especially vulnerable participants, from harm. Vulnerability is increasingly understood to be context specific, yet limited guidance is available regarding the vulnerability and agency of research participants in different cultural settings. This study aims to explore research participants' daily vulnerability and agency, and how these interact with participants' research experiences in their own words. Researchers' views and responses were also explored.

METHODS

A qualitative study was conducted around two scrub typhus research studies in northern Thailand. A thematic analysis was carried out on 42 semi-structured interviews with research participants, their families, researchers and key informants.

RESULTS

The majority of the research participants belonged to a hill tribe ethnic minority group. Common challenges were related to Thai language barriers, travel difficulties, uncertain legal status, unstable employment, lack of education and healthcare. We did not identify new vulnerabilities but we found that the extent of these vulnerabilities might be underestimated or even hidden from researchers in some cases. Despite these challenges people demonstrated agency in their daily lives and were often motivated and supported in this by family members. The majority of perceived research benefits were related to healthcare and gaining knowledge, while attending follow-up visits could be a burden for some.

CONCLUSIONS

Our approach to research in culturally and socioeconomically diverse settings should be more responsive to participants' specific vulnerabilities and abilities evidenced in their daily life, rather than attributing vulnerability on the basis of membership of pre-defined 'vulnerable groups'. Researchers need to be aware and responsive towards the challenges participants face locally in order to minimise the burdens of research participation whilst allowing participants to benefit from research.

Procalcitonin as a Candidate Biomarker for Malarial Infection and Severe Malaria: A Meta-Analysis

Procalcitonin (PCT), as a marker of malaria severity, remains to be investigated. The present study collated and compared the levels of PCT between patients with severe malaria, uncomplicated malaria, and control participants to assess their role in predicting malaria infection and disease severity. The systematic review was registered at PROSPERO with registration number CRD42021297243. The search for relevant studies that reported PCT in patients with malaria was performed in PubMed, Scopus, and Web of Science. The following meta-analyses were conducted; (1) the pooled mean PCT levels in patients with severe and uncomplicated malaria, and (2) the pooled mean difference in PCT levels between patients with severe and uncomplicated malaria. Fifteen studies were included for qualitative and quantitative syntheses. The meta-analysis results show that the pooled mean PCT levels in patients with uncomplicated malaria were 3.92 ng/mL (95% CI: 2.26-5.58 ng/mL, I²: 96.5, five studies), whereas the pooled mean PCT levels in patients with severe malaria were 14.13 ng/mL (95% CI: 8.75-19.5 ng/mL, I²: 92.6, six studies). The meta-analysis showed that patients with severe malaria had an equal mean of PCT compared to those with uncomplicated malaria when the random-effects model was used (p: 0.055, weighted mean difference: 6.93, 95% CI: -0.16-14.02, I²: 84.6%, four studies). There were probable correlations between the level of parasitemia, immunity level, and possibly bacterial or other parasitic co-infection that could affect the PCT level among different clinical severities of malaria. Therefore, the PCT level alone does not seem to be a suitable biomarker to discriminate the severe/uncomplicated or infected/uninfected cases. Further studies should investigate the increased PCT levels in combination with other markers in association with malaria infection and severity.

ACCURACY OF C-REACTIVE PROTEIN AND PROCALCITONIN FOR DIAGNOSING BACTERIAL INFECTIONS AMONG SUBJECTS WITH PERSISTENT FEVER IN THE TROPICS

Background

In low-resource settings, inflammatory biomarkers can help identify patients with acute febrile illness who do not require antibiotics. Their use has not been studied in persistent fever (defined as fever lasting for ≥7 days at presentation).

Methods

C-reactive protein (CRP) and procalcitonin (PCT) levels were measured in stored serum samples of patients with persistent fever prospectively enrolled in Cambodia, the Democratic Republic of Congo, Nepal, and Sudan. Diagnostic accuracy was assessed for identifying all bacterial infections and the subcategory of severe infections judged to require immediate antibiotics.

Results

Among 1838 participants, CRP and PCT levels were determined in 1777 (96.7%) and 1711 (93.1%) samples, respectively, while white blood cell (WBC) count was available for 1762 (95.9%). Areas under the receiver operating characteristic curve for bacterial infections were higher for CRP (0.669) and WBC count (0.651) as compared with PCT (0.600; P <.001). Sensitivity for overall and severe bacterial infections was 76.3% (469/615) and 88.2% (194/220) for CRP >10 mg/L, 62.4% (380/609) and 76.8% (169/220) for PCT >0.1 µg/L, and 30.5% (184/604) and 43.7% (94/215) for WBC >11 000/µL, respectively. Initial CRP level was <10 mg/L in 45% of the participants who received antibiotics at first presentation.

Conclusions

In patients with persistent fever, CRP and PCT showed higher sensitivity for bacterial infections than WBC count, applying commonly used cutoffs for normal values. A normal CRP value excluded the vast majority of severe infections and could therefore assist in deciding whether to withhold empiric antibiotics after cautious clinical assessment.

A time-course comparative clinical and immune response evaluation study between the human pathogenic Orientia tsutsugamushi strains: Karp and Gilliam in a rhesus macaque (Macaca mulatta) model

BACKGROUND

Scrub typhus is a vector-borne febrile illness caused by Orientia tsutsugamushi transmitted by the bite of Trombiculid mites. O. tsutsugamushi has a high genetic diversity and is increasingly recognized to have a wider global distribution than previously assumed.

METHODOLOGY/PRINCIPLE FINDINGS

We evaluated the clinical outcomes and host immune responses of the two most relevant human pathogenic strains of O. tsutsugamushi; Karp (n = 4) and Gilliam (n = 4) in a time-course study over 80 days post infection (dpi) in a standardized scrub typhus non-human primate rhesus macaque model. We observed distinct features in clinical progression and immune response between the two strains; Gilliam-infected macaques developed more pronounced systemic infection characterized by an earlier onset of bacteremia, lymph node enlargement, eschar lesions and higher inflammatory markers during the acute phase of infection, when compared to the Karp strain. C-reactive protein (CRP) plasma levels, interferon gamma (IFN-γ, interleukin-1 receptor antagonist (IL-1ra), IL-15 serum concentrations, CRP/IL10- and IFN-γ/IL-10 ratios correlated positively with bacterial load in blood, implying activation of the innate immune response and preferential development of a T helper-type 1 immune response. The O. tsutsugamushi-specific immune memory responses in cells isolated from skin and lymph nodes at 80 dpi were more markedly elevated in the Gilliam-infected macaques than in the Karp-infected group. The comparative cytokine response dynamics of both strains revealed significant up-regulation of IFN-γ, tumor necrosis factor (TNF), IL-15, IL-6, IL-18, regulatory IL-1ra, IL-10, IL-8 and granulocyte-colony-stimulating factor (G-CSF). These data suggest that the clinical outcomes and host immune responses to scrub typhus could be associated with counter balancing effects of pro- and anti-inflammatory cytokine-mediated responses. Currently, no data on characterized time-course comparisons of O. tsutsugamushi strains regarding measures of disease severity and immune response is available. Our study provides evidence for the strain-specificity of host responses in scrub typhus, which supports our understanding of processes at the initial inoculation site (eschar), systemic disease progression, protective and/or pathogenic host immune mechanisms and cellular immune memory function.

CONCLUSIONS/SIGNIFICANCE

This study characterised an improved intradermal rhesus macaque challenge model for scrub typhus, whereby the Gilliam strain infection associated with higher disease severity in the rhesus macaque model than the previous Karp strain infection. Difficulties associated with inoculum quantitation for obligate-intracellular bacteria were overcome by using functional inoculum titrations in outbred mice. The Gilliam-based rhesus macaque model provides improved endpoint measurements and contributes towards the identification of correlates of protection for future vaccine development.

Antimicrobial Stewardship in Tropical Infectious Diseases: Focusing on Dengue and Malaria

Acute undifferentiated febrile illness (AUFI) is the presenting symptom of various tropical and infectious diseases. Viral infection is generally the most common cause of AUFI, accounting for 8–11.8% of cases; thus, antibiotics might be unnecessary. Dengue and malaria are common tropical infectious diseases requiring effective supportive treatment and antimalarial agents, respectively. The uncertainty of early diagnosis results in widespread empirical antimicrobial treatment in high -income as well as in low-and middle-income countries. Although rapid diagnostic tests (RDTs) have been shown to limit antibiotic prescriptions in dengue and malaria, we observed a wide range of antibiotic prescriptions for 13–92.7% of cases in previous literature, particularly in RDT-negative malaria cases. Given several RDT limitations, antimicrobial stewardship (AMS) appears to be an effective strategy for controlling unnecessary antibiotic use and antimicrobial resistance (AMR) prevention. This program should be endorsed by a multidisciplinary team in tropical diseases to control collateral damage of inappropriate antimicrobial use. Empirical antibiotic treatment should be administered based on clinical judgement, microbiological evidence, and local epidemiological data. Rapid termination of antibiotic therapy, including disease control or elimination, is the mainstay of AMS in tropical diseases. Local and international sectors should implement an AMS programme to reduce AMR in the Tropics.

Systematic Surveillance of Rickettsial Diseases in 27 Hospitals from 26 Provinces throughout Vietnam

In Vietnam, the public health burden of rickettsial infections continues to be underestimated due to knowledge gaps in the epidemiology of these diseases. We conducted a systematic study among 27 hospitals from 26 provinces in eight ecological regions throughout Vietnam to investigate the prevalence, distribution, and clinical characteristics of rickettsial diseases. We recruited 1834 patients in the study from April 2018 to October 2019. The findings showed that rickettsial diseases were common among undifferentiated febrile patients, with 564 (30.8%) patients positive by qPCR for scrub typhus, murine typhus or spotted fever. Scrub typhus (484, 85.8%) was the most common rickettsial disease, followed by murine typhus (67, 11.9%) and spotted fever (10, 1.8%). Rickettsial diseases were widely distributed in all regions of Vietnam and presented with nonspecific clinical manifestations.

Rickettsial Infections Are Neglected Causes of Acute Febrile Illness in Teluk Intan, Peninsular Malaysia

Rickettsial infections are among the leading etiologies of acute febrile illness in Southeast Asia. However, recent data from Malaysia are limited. This prospective study was conducted in Teluk Intan, Peninsular Malaysia, during January to December 2016. We recruited 309 hospitalized adult patients with acute febrile illness. Clinical and biochemistry data were obtained, and patients were stratified into mild and severe infections based on the sepsis-related organ failure (qSOFA) scoring system. Diagnostic assays including blood cultures, real-time PCR, and serology (IFA and MAT) were performed. In this study, pathogens were identified in 214 (69%) patients, of which 199 (93%) patients had a single etiology, and 15 (5%) patients had >1 etiologies. The top three causes of febrile illness requiring hospitalization in this Malaysian study were leptospirosis (68 (32%)), dengue (58 (27%)), and rickettsioses (42 (19%)). Fifty-five (18%) patients presented with severe disease with a qSOFA score of ≥2. Mortality was documented in 38 (12%) patients, with the highest seen in leptospirosis (16 (42%)) followed by rickettsiosis (4 (11%)). While the significance of leptospirosis and dengue are recognized, the impact of rickettsial infections in Peninsular Malaysia remains under appreciated. Management guidelines for in-patient care with acute febrile illness in Peninsular Malaysia are needed.

Simple clinical and laboratory predictors to improve empirical treatment strategies in areas of high scrub typhus and dengue endemicity, central Vietnam

Background

Dengue fever is highly endemic in Vietnam, but scrub typhus—although recognized as an endemic disease—remains underappreciated. These diseases together are likely to account for more than half of the acute undifferentiated fever burden in Vietnam. Scrub typhus (ST) is a bacterial disease requiring antimicrobial treatment, while dengue fever (DF) is of viral etiology and does not. The access to adequate diagnostics and the current understanding of empirical treatment strategies for both illnesses remain limited. In this study we aimed to contribute to the clinical decision process in the management of these two important etiologies of febrile illness in Vietnam.

Methods

Using retrospective data from 221 PCR-confirmed scrub typhus cases and 387 NS1 protein positive dengue fever patients admitted to five hospitals in Khanh Hoa province (central Vietnam), we defined predictive characteristics for both diseases that support simple clinical decision making with potential to inform decision algorithms in future. We developed models to discriminate scrub typhus from dengue fever using multivariable logistic regression (M-LR) and classification and regression trees (CART). Regression trees were developed for the entire data set initially and pruned, based on cross-validation. Regression models were developed in a training data set involving 60% of the total sample and validated in the complementary subsample. Probability cut points for the distinction between scrub typhus and dengue fever were chosen to maximise the sum of sensitivity and specificity.

Results

Using M-LR, following seven predictors were identified, that reliably differentiate ST from DF; eschar, regional lymphadenopathy, an occupation in nature, increased days of fever on admission, increased neutrophil count, decreased ratio of neutrophils/lymphocytes, and age over 40. Sensitivity and specificity of predictions based on these seven factors reached 93.7% and 99.5%, respectively. When excluding the “eschar” variable, the values dropped to 76.3% and 92.3%, respectively.

The CART model generated one further variable; increased days of fever on admission, when eschar was included, the sensitivity and specificity was 95% and 96.9%, respectively. The model without eschar involved the following six variables; regional lymphadenopathy, increased days of fever on admission, increased neutrophil count, increased lymphocyte count, platelet count ≥ 47 G/L and age over 28 years as predictors of ST and provided a sensitivity of 77.4% and a specificity of 90.7%.

Conclusions

The generated algorithms contribute to differentiating scrub typhus from dengue fever using basic clinical and laboratory parameters, supporting clinical decision making in areas where dengue and scrub typhus are co-endemic in Vietnam.

Dengue fever is highly endemic in Vietnam, while scrub typhus is recognized as a re-emerging neglected disease. Both diseases are likely to account for more than half of the acute undifferentiated fever burden in Vietnam. However, scrub typhus is a bacterial disease requiring antimicrobial treatment, while dengue fever—of viral etiology—does not. Misdiagnosis and treatment delays cause potentially severe or fatal complications among scrub typhus patients, even though it is easily treatable. In this study, we used simple clinical and laboratory markers, which were identified upon admission of 221 PCR-confirmed scrub typhus cases and 387 NS1-positive dengue fever patients from Khanh Hoa province to identify the differences between scrub typhus and dengue. We found seven predictors that served to construct a simple clinical decision tree, holding great potential to distinguish scrub typhus from dengue using readily available clinical or laboratory findings. These predictors can strongly support medical staff in identifying scrub typhus cases from dengue, without using sophisticated diagnostic tests, and could improve the quality of diagnoses and appropriate treatment strategies at the primary health care level–especially in areas where scrub typhus and dengue fever are co-endemic in Vietnam and many parts of Asia and where diagnostic tests are not readily available.

Etiological spectrum of persistent fever in the tropics and predictors of ubiquitous infections: a prospective four-country study with pooled analysis

BACKGROUND

Persistent fever, defined as fever lasting for 7 days or more at first medical evaluation, has been hardly investigated as a separate clinical entity in the tropics. This study aimed at exploring the frequencies and diagnostic predictors of the ubiquitous priority (i.e., severe and treatable) infections causing persistent fever in the tropics.

METHODS

In six different health settings across four countries in Africa and Asia (Sudan, Democratic Republic of Congo [DRC], Nepal, and Cambodia), consecutive patients aged 5 years or older with persistent fever were prospectively recruited from January 2013 to October 2014. Participants underwent a reference diagnostic workup targeting a pre-established list of 12 epidemiologically relevant priority infections (i.e., malaria, tuberculosis, HIV, enteric fever, leptospirosis, rickettsiosis, brucellosis, melioidosis, relapsing fever, visceral leishmaniasis, human African trypanosomiasis, amebic liver abscess). The likelihood ratios (LRs) of clinical and basic laboratory features were determined by pooling all cases of each identified ubiquitous infection (i.e., found in all countries). In addition, we assessed the diagnostic accuracy of five antibody-based rapid diagnostic tests (RDTs): Typhidot Rapid IgM, Test-it^TM Typhoid IgM Lateral Flow Assay, and SD Bioline Salmonella typhi IgG/IgM for Salmonella Typhi infection, and Test-it^TM Leptospira IgM Lateral Flow Assay and SD Bioline Leptospira IgG/IgM for leptospirosis.

RESULTS

A total of 1922 patients (median age: 35 years; female: 51%) were enrolled (Sudan, n = 667; DRC, n = 300; Nepal, n = 577; Cambodia, n = 378). Ubiquitous priority infections were diagnosed in 452 (23.5%) participants and included malaria 8.0% (n = 154), tuberculosis 6.7% (n = 129), leptospirosis 4.0% (n = 77), rickettsiosis 2.3% (n = 44), enteric fever 1.8% (n = 34), and new HIV diagnosis 0.7% (n = 14). The other priority infections were limited to one or two countries. The only features with a positive LR ≥ 3 were diarrhea for enteric fever and elevated alanine aminotransferase level for enteric fever and rickettsiosis. Sensitivities ranged from 29 to 67% for the three RDTs targeting S. Typhi and were 9% and 16% for the two RDTs targeting leptospirosis. Specificities ranged from 86 to 99% for S. Typhi detecting RDTs and were 96% and 97% for leptospirosis RDTs.

CONCLUSIONS

Leptospirosis, rickettsiosis, and enteric fever accounted each for a substantial proportion of the persistent fever caseload across all tropical areas, in addition to malaria, tuberculosis, and HIV. Very few discriminative features were however identified, and RDTs for leptospirosis and Salmonella Typhi infection performed poorly. Improved field diagnostics are urgently needed for these challenging infections.

TRIAL REGISTRATION

NCT01766830 at ClinicalTrials.gov.

Role of Diagnostics in Epidemiology, Management, Surveillance, and Control of Leptospirosis

A One Health approach to the epidemiology, management, surveillance, and control of leptospirosis relies on accessible and accurate diagnostics that can be applied to humans and companion animals and livestock. Diagnosis should be multifaceted and take into account exposure risk, clinical presentation, and multiple direct and/or indirect diagnostic approaches. Methods of direct detection of Leptospira spp. include culture, histopathology and immunostaining of tissues or clinical specimens, and nucleic acid amplification tests (NAATs). Indirect serologic methods to detect leptospiral antibodies include the microscopic agglutination test (MAT), the enzyme-linked immunosorbent assay (ELISA), and lateral flow methods. Rapid diagnostics that can be applied at the point-of-care; NAAT and lateral flow serologic tests are essential for management of acute infection and control of outbreaks. Culture is essential to an understanding of regional knowledge of circulating strains, and we discuss recent improvements in methods for cultivation, genomic sequencing, and serotyping. We review the limitations of NAATs, MAT, and other diagnostic approaches in the context of our expanding understanding of the diversity of pathogenic Leptospira spp. Novel approaches are needed, such as loop mediated isothermal amplification (LAMP) and clustered regularly interspaced short palindromic repeats (CRISPR)-based approaches to leptospiral nucleic acid detection.

Defining the burden of febrile illness in rural South and Southeast Asia: an open letter to announce the launch of the Rural Febrile Illness project

In rural areas of South and Southeast Asia malaria is declining but febrile illnesses still account for substantial morbidity and mortality. Village health workers (VHWs) are often the first point of contact with the formal health system, and for patients with febrile illnesses they can provide early diagnosis and treatment of malaria. However, for the majority of febrile patients, VHWs lack the training, support and resources to provide further care. Consequently, treatable bacterial illnesses are missed, antibiotics are overused and poorly targeted, and patient attendance wanes along with declining malaria.

This Open Letter announces the start of a new initiative, the Rural Febrile Illness (RFI) project, the first in a series of projects to be implemented as part of the South and Southeast Asian Community-based Trials Network (SEACTN) research programme. This multi-country, multi-site project will run in Bangladesh, Cambodia, Lao PDR, Thailand, and Myanmar. It will define the epidemiological baseline of febrile illness in nine remote and underserved areas of Asia where malaria endemicity is declining and access to health services is limited.

The RFI project aims to determine the incidence, causes and outcomes of febrile illness; understand the opportunities, barriers and appetite for adjustment of the role of VHWs to include management of non-malarial febrile illnesses; and establish a network of community healthcare providers and facilities capable of implementing interventions designed to triage, diagnose and treat patients presenting with febrile illnesses within these communities in the future.

Opportunities and challenges to accurate diagnosis and management of acute febrile illness in adults and adolescents: A review

Acute febrile illnesses are common reasons to seek healthcare globally. They can be caused by diverse infectious diseases which require complex diagnostics. Current clinical guidelines provide guidance on how to manage severe illness, common localizing infections like pneumonia and urinary tract infections, as well as malaria. How to manage other cases of acute febrile illness is less clear and is the focus of this review. Without an etiologic diagnosis, clinicians frequently prescribe empiric antibiotics that may be unnecessary or inadequate. We reviewed recent studies on the etiology of acute febrile illnesses in adults and adolescents that employed multiple diagnostic modalities, including rapid diagnostic tests, serologies, and polymerase chain reaction. Although studies and etiologies were heterogenous, we enumerated the causes of febrile illness in these studies. Possible improvements in clinical decision-making algorithms are discussed.

The Early Diagnosis of Scrub Typhus by Metagenomic Next-Generation Sequencing

Introduction: Scrub typhus is a mite-borne infection widespread in Southeast Asia, with clinical symptoms such as fever, chills, skin rash, eschar at the bite site, and other signs of acute febrile illness. The Rickettsia pathogen (Orientia tsutsugamushi) is always difficult to be diagnosed at an early stage by traditional clinical diagnostic methods, especially for patients without typical eschar. This greatly increases the mortality of patients with scrub typhus. A new approach should be introduced to improve its clinical diagnosis.

Methods: During May 2018 to March 2021, 13 samples from 10 patients with suspected scrub typhus were collected. Metagenomic next-generation sequencing (mNGS) and other diagnostic methods (including serology using Weil–Felix reaction and indirect immunofluorescence test (IIFT) for scrub typhus and respiratory tract profile IgM as well as culture for routine bacteria) were used to identify the pathogens in this study.

Results: The results of mNGS were all positive, with mapped reads of O. tsutsugamushi ranging from 1 to 460. Eight patients (80%) were diagnosed as scrub typhus. The other two were diagnosed as suspected scrub typhus due to the limited number of reads of the pathogen (one and two, respectively). According to clinical evidences, nine of the 10 patients were finally diagnosed as scrub typhus, except for patient 9 (suspected scrub typhus by mNGS with one specific reads of the pathogen) diagnosed as acute exacerbation of chronic obstructive pulmonary disease. For the five scrub typhus patients without typical eschar, mNGS gave all positive results (4–460 specific reads). For other methods, only Weil–Felix reaction of one patient detected the pathogen. In addition, the respiratory tract profile (IgM) detected various pathogens, but all were confirmed to be false positive.

Conclusions: mNGS performed better than conventional clinical methods to early diagnose scrub typhus. This approach can be routinely carried out for early and precise diagnosis in clinical infections, especially for those hard to be identified by traditional diagnostic methods.

Systematic review of the scrub typhus treatment landscape: Assessing the feasibility of an individual participant-level data (IPD) platform

Background

Scrub typhus is an acute febrile illness caused by intracellular bacteria from the genus Orientia. It is estimated that one billion people are at risk, with one million cases annually mainly affecting rural areas in Asia-Oceania. Relative to its burden, scrub typhus is understudied, and treatment recommendations vary with poor evidence base. These knowledge gaps could be addressed by establishing an individual participant-level data (IPD) platform, which would enable pooled, more detailed and statistically powered analyses to be conducted. This study aims to assess the characteristics of scrub typhus treatment studies and explore the feasibility and potential value of developing a scrub typhus IPD platform to address unanswered research questions.

Methodology/principal findings

We conducted a systematic literature review looking for prospective scrub typhus clinical treatment studies published from 1998 to 2020. Six electronic databases (Ovid Embase, Ovid Medline, Ovid Global Health, Cochrane Library, Scopus, Global Index Medicus), ClinicalTrials.gov, and WHO ICTRP were searched. We extracted data on study design, treatment tested, patient characteristics, diagnostic methods, geographical location, outcome measures, and statistical methodology.

Among 3,100 articles screened, 127 were included in the analysis. 12,079 participants from 12 countries were enrolled in the identified studies. ELISA, PCR, and eschar presence were the most commonly used diagnostic methods. Doxycycline, azithromycin, and chloramphenicol were the most commonly administered antibiotics. Mortality, complications, adverse events, and clinical response were assessed in most studies. There was substantial heterogeneity in the diagnostic methods used, treatment administered (including dosing and duration), and outcome assessed across studies. There were few interventional studies and limited data collected on specific groups such as children and pregnant women.

Conclusions/significance

There were a limited number of interventional trials, highlighting that scrub typhus remains a neglected disease. The heterogeneous nature of the available data reflects the absence of consensus in treatment and research methodologies and poses a significant barrier to aggregating information across available published data without access to the underlying IPD. There is likely to be a substantial amount of data available to address knowledge gaps. Therefore, there is value for an IPD platform that will facilitate pooling and harmonisation of currently scattered data and enable in-depth investigation of priority research questions that can, ultimately, inform clinical practice and improve health outcomes for scrub typhus patients.

Scrub typhus is a febrile illness most commonly found in rural tropical areas. It is caused by a Gram-negative bacteria belonging to the family Rickettsiaceae and transmitted by mites when they feed on vertebrates. There is an estimate of one million cases annually, with an estimated one billion people at risk, mostly in Asia-Oceania. But relative to the scale of the problem, scrub typhus is largely understudied. Evidence-based treatment recommendations by policymakers vary or are non-existent. We searched databases and registries for prospective scrub typhus clinical treatment studies published from 1998 to 2020 and reviewed them. Data from clinical trials and particularly for specific groups, such as pregnant women and children, were minimal. The methods used to measure treatment efficacy were heterogeneous, making it difficult to directly compare or conduct a meta-analysis based on aggregated data. One way to improve the current level of evidence would be by pooling and analysing individual participant-level data (IPD), i.e. the raw data from individual participants in completed studies. This review demonstrated that there is scope for developing a database for individual participant data to enable more detailed analyses. IPD meta-analyses could be a way to address knowledge gaps such as optimum dosing for children and pregnant women.

Longitudinal analysis to characterize classes and subclasses of antibody responses to recombinant receptor-binding protein (RBD) of SARS-CoV-2 in COVID-19 patients in Thailand

Serological assays to detect antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might contribute to confirming the suspected coronavirus disease 2019 (COVID-19) in patients not detected with molecular assays. Human antibodies that target the host angiotensin-converting enzyme 2-binding domain of the viral spike protein are a target for serodiagnosis and therapeutics. This study aimed to characterize the classes and subclasses of antibody responses to a recombinant receptor-binding protein (RBD) of SARS-CoV-2 in COVID-19 patients and investigated the reactivity of these antibodies in patients with other tropical infections and healthy individuals in Thailand. ELISAs for IgM, IgA, IgG and IgG subclasses based on RBD antigen were developed and tested with time series of 27 serum samples from 15 patients with COVID-19 and 60 samples from pre-COVID-19 outbreaks including acute dengue fever, murine typhus, influenza, leptospirosis and healthy individuals. Both RBD-specific IgA and IgG were detected in only 21% of the COVID-19 patients in the acute phase. The median IgA and IgG levels were significantly higher in the convalescent serum sample compared to the acute serum sample (P < 0.05). We observed the highest correlation between levels of IgG and IgA (rho = 0. 92). IgG1 and IgG3 were the major IgG subclasses detected in SARS-CoV-2 infection. Only acute IgG3 level was negatively associated with viral detection based on RT-PCR of ORF1ab gene (rho = -0.57). The median IgA and IgG levels in convalescence sera of COVID-19 patients were significantly higher than healthy individuals and convalescent sera of other febrile infectious patients. The analyses of antibody classes and subclasses provide insights into human immune responses against SARS-CoV-2 during natural infection and interpretation of antibody assays.

Spotted Fever Group Rickettsiae among Children with Acute Febrile Illness, in Gorakhpur, India

Seasonal outbreaks of acute encephalitis syndrome have been occurring in Gorakhpur division in the Indian state of Uttar Pradesh during monsoon and post-monsoon months. Orientia tsutsugamushi was identified as the major aetiology of these outbreaks. Orientia tsutsugamushi was also identified as one of the important aetiology of febrile illness among children attending peripheral health facilities. The present study was undertaken to detect antibodies against spotted fever group rickettsiae (SFGR) and typhus group rickettsiae (TGR) among children with acute febrile illness presenting at peripheral health facilities in Gorakhpur district. Of the 224 blood samples tested, SFGR infection was detected in 13 (6%) patients. None of the samples tested positive for TGR.

The good and the bad: using C reactive protein to distinguish bacterial from non-bacterial infection among febrile patients in low-resource settings

C reactive protein (CRP), a marker for the presence of an inflammatory process, is the most extensively studied marker for distinguishing bacterial from non-bacterial infections in febrile patients. A point-of-care test for bacterial infections would be of particular use in low-resource settings where other laboratory diagnostics are not always available, antimicrobial resistance rates are high and bacterial infections such as pneumonia are a leading cause of death. This document summarises evidence on CRP testing for bacterial infections in low-income and middle-income countries (LMICs). With a push for universal health coverage and prevention of antimicrobial resistance, it is important to understand if CRP might be able to do the job. The use of CRP polarised the global health community and the aim of this document is to summarise the ‘good and the bad’ of CRP in multiple settings in LMICs. In brief, the literature that was reviewed suggests that CRP testing may be beneficial in low-resource settings to improve rational antibiotic use for febrile patients, but the positive predictive value is insufficient to allow it to be used alone as a single tool. CRP testing may be best used as part of a panel of diagnostic tests and algorithms. Further studies in low-resource settings, particularly with regard to impact on antibiotic prescribing and cost-effectiveness of CRP testing, are warranted.

Procalcitonin (PCT)-guided antibiotic stewardship in Asia-Pacific countries: adaptation based on an expert consensus meeting

Introduction Recently, an expert consensus on optimal use of procalcitonin (PCT)-guided antibiotic stewardship was published focusing mainly on Europe and the United States. However, for Asia-Pacific countries, recommendations may need adaptation due to differences in types of infections, available resources and standard of clinical care. Methods Practical experience with PCT-guided antibiotic stewardship was discussed among experts from different countries, reflecting on the applicability of the proposed Berlin consensus algorithms for Asia-Pacific. Using a Delphi process, the group reached consensus on two PCT algorithms for the critically ill and the non-critically ill patient populations. Results The group agreed that the existing evidence for PCT-guided antibiotic stewardship in patients with acute respiratory infections and sepsis is generally valid also for Asia-Pacific countries, in regard to proposed PCT cut-offs, emphasis on diagnosis, prognosis and antibiotic stewardship, overruling criteria and inevitable adaptations to clinical settings. However, the group noted an insufficient database on patients with tropical diseases currently limiting the clinical utility in these patients. Also, due to lower resource availabilities, biomarker levels may be measured less frequently and only when changes in treatment are highly likely. Conclusions Use of PCT to guide antibiotic stewardship in conjunction with continuous education and regular feedback to all stakeholders has high potential to improve the utilization of antibiotic treatment also in Asia-Pacific countries. However, there is need for adaptations of existing algorithms due to differences in types of infections and routine clinical care. Further research is needed to understand the optimal use of PCT in patients with tropical diseases.

Effects of Accounting for Interval-Censored Antibody Titer Decay on Seroincidence in a Longitudinal Cohort Study of Leptospirosis

Accurate measurements of seroincidence are critical for infections undercounted by reported cases, such as influenza, arboviral diseases, and leptospirosis. However, conventional methods of interpreting paired serological samples do not account for antibody titer decay, resulting in underestimated seroincidence rates. To improve interpretation of paired sera, we modeled exponential decay of interval-censored microscopic agglutination test titers using a historical data set of leptospirosis cases traced to a point source exposure in Italy in 1984. We then applied that decay rate to a longitudinal cohort study conducted in a high-transmission setting in Salvador, Brazil (2013-2015). We estimated a decay constant of 0.926 (95% confidence interval: 0.918, 0.934) titer dilutions per month. Accounting for decay in the cohort increased the mean infection rate to 1.21 times the conventionally defined rate over 6-month intervals (range, 1.10-1.36) and 1.82 times that rate over 12-month intervals (range, 1.65-2.07). Improved estimates of infection in longitudinal data have broad epidemiologic implications, including comparing studies with different sampling intervals, improving sample size estimation, and determining risk factors for infection and the role of acquired immunity. Our method of estimating and accounting for titer decay is generalizable to other infections defined using interval-censored serological assays.

Defining the burden of febrile illness in rural South and Southeast Asia: an open letter to announce the launch of the Rural Febrile Illness project

In rural areas of South and Southeast Asia malaria is declining but febrile illnesses still account for substantial morbidity and mortality. Village health workers (VHWs) are often the first point of contact with the formal health system, and for patients with febrile illnesses they can provide early diagnosis and treatment of malaria. However, for the majority of febrile patients, VHWs lack the training, support and resources to provide further care. Consequently, treatable bacterial illnesses are missed, antibiotics are overused and poorly targeted, and patient attendance wanes along with declining malaria. This Open Letter announces the start of a new initiative, the Rural Febrile Illness (RFI) project, the first in a series of projects to be implemented as part of the South and Southeast Asian Community-based Trials Network (SEACTN) research programme. This multi-country, multi-site project will begin in Bangladesh, Cambodia, Lao PDR, and Myanmar and will define the epidemiological baseline of febrile illness in five remote and underserved areas of Asia where malaria endemicity is declining and access to health services is limited. The RFI project aims to determine the incidence, causes and outcomes of febrile illness; understand the opportunities, barriers and appetite for adjustment of the role of VHWs to include management of non-malarial febrile illnesses; and establish a network of community healthcare providers and facilities capable of implementing interventions designed to triage, diagnose and treat patients presenting with febrile illnesses within these communities in the future.

Laboratory Diagnosis of Leptospirosis

The diagnosis of leptospirosis depends on specific laboratory tests because nonspecific and diverse clinical manifestations make clinical diagnosis difficult and it is easily confused with other infectious diseases in the tropics. Suitable laboratory diagnostic tests vary depending on the stage of the disease, requiring the combination of diagnostic tests using appropriate specimens at each disease stage.

Infection Manager System (IMS) as a new hemocytometry-based bacteremia detection tool: A diagnostic accuracy study in a malaria-endemic area of Burkina Faso

BACKGROUND

New hemocytometric parameters can be used to differentiate causes of acute febrile illness (AFI). We evaluated a software algorithm-Infection Manager System (IMS)-which uses hemocytometric data generated by Sysmex hematology analyzers, for its accuracy to detect bacteremia in AFI patients with and without malaria in Burkina Faso. Secondary aims included comparing the accuracy of IMS with C-reactive protein (CRP) and procalcitonin (PCT).

METHODS

In a prospective observational study, patients of ≥ three-month-old (range 3 months- 90 years) presenting with AFI were enrolled. IMS, blood culture and malaria diagnostics were done upon inclusion and additional diagnostics on clinical indication. CRP, PCT, viral multiplex PCR on nasopharyngeal swabs and bacterial- and malaria PCR were batch-tested retrospectively. Diagnostic classification was done retrospectively using all available data except IMS, CRP and PCT results.

FINDINGS

A diagnosis was affirmed in 549/914 (60.1%) patients and included malaria (n = 191) bacteremia (n = 69), viral infections (n = 145), and malaria-bacteremia co-infections (n = 47). The overall sensitivity, specificity, and negative predictive value (NPV) of IMS for detection of bacteremia in patients of ≥ 5 years were 97.0% (95% CI: 89.8-99.6), 68.2% (95% CI: 55.6-79.1) and 95.7% (95% CI: 85.5-99.5) respectively, compared to 93.9% (95% CI: 85.2-98.3), 39.4% (95% CI: 27.6-52.2), and 86.7% (95% CI: 69.3-96.2) for CRP at ≥20mg/L. The sensitivity, specificity and NPV of PCT at 0.5 ng/ml were lower at respectively 72.7% (95% CI: 60.4-83.0), 50.0% (95% CI: 37.4-62.6) and 64.7% (95% CI: 50.1-77.6) The diagnostic accuracy of IMS was lower among malaria cases and patients <5 years but remained equal to- or higher than the accuracy of CRP.

INTERPRETATION

IMS is a new diagnostic tool to differentiate causes of AFI. Its high NPV for bacteremia has the potential to improve antibiotic dispensing practices in healthcare facilities with hematology analyzers. Future studies are needed to evaluate whether IMS, combined with malaria diagnostics, may be used to rationalize antimicrobial prescription in malaria endemic areas.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02669823) https://clinicaltrials.gov/ct2/show/NCT02669823.

Value of C-reactive protein in differentiating viral from bacterial aetiologies in patients with non-malaria acute undifferentiated fever in tropical areas: a meta-analysis and individual patient data study

C-reactive protein (CRP) is used to discriminate common bacterial and viral infections, but its utility in tropical settings remains unknown. We performed a meta-analysis of studies performed in Asia and Africa. First, mean CRP levels for specific tropical infections were calculated. Thereafter, individual patient data (IPD) from patients with non-malarial undifferentiated fever (NMUF) who were tested for viral and bacterial pathogens were analysed, calculating separate cut-off values and their performance in classifying viral or bacterial disease. Mean CRP levels of 7307 patients from 13 countries were dengue 12.0 mg/l (standard error [SE] 2.7), chikungunya 41.0 mg/l (SE 19.5), influenza 15.9 mg/l (SE 6.3), Crimean-Congo haemorrhagic fever 9.7 mg/l (SE 4.7), Salmonella 61.9 mg/l (SE 5.4), Rickettsia 61.3 mg/l (SE 8.8), Coxiella burnetii 98.7 mg/l (SE 44.0) and Leptospira infections 113.8 mg/l (SE 23.1). IPD analysis of 1059 NMUF patients ≥5 y of age showed CRP <10 mg/l had 52% sensitivity (95% confidence interval [CI] 48 to 56) and 95% specificity (95% CI 93 to 97) to detect viral infections. CRP >40 mg/l had 74% sensitivity (95% CI 70 to 77) and 84% specificity (95% CI 81 to 87) to identify bacterial infections. Compared with routine care, the relative risk for incorrect classification was 0.64 (95% CI 0.55 to 0.75) and the number needed to test for one extra correctly classified case was 8 (95% CI 6 to 12). A two cut-off value CRP test may help clinicians to discriminate viral and bacterial aetiologies of NMUF in tropical areas.

Clinical Symptoms of Dengue Infection among Patients from a Non-Endemic Area and Potential for a Predictive Model: A Multiple Logistic Regression Analysis and Decision Tree

Under-recognition of dengue infection may lead to increased morbidity and mortality, whereas early detection is shown to help improve patient outcomes. Recent incidence and outbreak reports of dengue virus in the United States and other temperate regions where dengue was not typically seen have raised concerns regarding appropriate diagnosis and management by healthcare providers unfamiliar with the disease. This study aimed to describe self-reported clinical symptoms of dengue fever in a non-endemic cohort and to establish a clinically useful predictive algorithm based on presenting features that can assist in the early evaluation of potential dengue infection. Volunteers who experienced febrile illness while traveling in dengue-endemic countries were recruited for this study. History of illness and blood samples were collected at enrollment. Participants were classified as dengue naive or dengue exposed based on neutralizing antibody titers. Statistical analysis was performed to compare characteristics between the two groups. A regression model including joint/muscle/bone pain, rash, dyspnea, and rhinorrhea predicts dengue infection with 78% sensitivity, 63% specificity, 80% positive predictive value, and 61% negative predictive value. A decision tree model including joint/muscle/bone pain, dyspnea, and rash yields 77% sensitivity and 67% specificity. Diagnosis of dengue fever is challenging because of the nonspecific nature of clinical presentation. A sensitive predicting model can be helpful to triage suspected dengue infection in the non-endemic setting, but specificity requires additional testing including laboratory evaluation.

Utility of a Simple Scoring System in Differentiating Bacterial Infections in Cases of Fever of Unknown Origin

BACKGROUND

Infectious disease is the leading cause of fever of unknown origin (FUO). Serum inflammatory markers historically used to diagnose bacterial infection have sufficient diagnostic sensitivity but low specificity. This study aimed to develop a simple scoring system for differentiating bacterial infections from other causes of early-stage FUO.

METHODS

This study included a retrospective cohort of patients presenting with FUO at the Huashan Hospital (January 2014 to June 2017). The diagnostic utility of serum inflammatory markers for bacterial infection was evaluated using the receiver operating characteristic (ROC) curve analysis. Relevant markers were subsequently measured prospectively in a separate cohort of FUO patients (December 2017 to May 2019). A scoring system was based on inflammatory markers and other test results.

RESULTS

Bacterial infection was identified in 34% of patients in the retrospective cohort. The area under the ROC curve (AUC) was 0.644 (95% confidence interval [CI], .595-.693) for C-reactive protein, 0.624 (95% CI, .573-.675) for procalcitonin, and 0.646 (95% CI, .595-.697) for serum ferritin (SF) in diagnosing bacterial infection. Bacterial infection was found in 29% of cases in the prospective cohort. A model based on serum amyloid A (SAA) and SF levels and neutrophil percentage yielded an AUC of 0.775 (95% CI, .695-.854). Validation analysis indicated lower probability (<15%) of bacterial infection for patients with a score <16.5 points.

CONCLUSIONS

A scoring system based on SAA and SF levels and neutrophil percentage can help distinguish bacterial infection from other causes of FUO, potentially reducing antibiotic use.

Usefulness of C-Reactive Protein and Other Host BioMarker Point-of-Care Tests in the Assessment of Non-Malarial Acute Febrile Illnesses: A Systematic Review with Meta-Analysis

In low- and middle-income countries, in resource-limited settings, the implementation of diagnostic tools discriminating bacterial from nonbacterial fever is a matter of primary concern. The introduction of malaria rapid diagnostic tests highlighted the need for point-of-care tests (POCTs) supporting clinical decision-making for non-malarial febrile illnesses. The purpose of this work was to review the use of host biomarker POCTs for the assessment of acute non-malarial fever in resource-constraint settings. Specific objectives were as follows: 1) to estimate the accuracy of such tests in differentiating fever of bacterial from nonbacterial origin and 2) to assess the impact of host biomarkers on antibiotic prescription and clinical outcome. We conducted a systematic review searching PubMed, Embase, the Cochrane Library, and Bireme. The protocol was registered with PROSPERO (n CRD42019141735). Data on the accuracy of C-reactive protein (CRP) for the detection of bacterial infections were meta-analyzed using the hierarchical summary receiver operating characteristic model, obtaining a summary ROC (SROC). We identified 2,192 articles, eight of which were included in the review. Among the different biomarkers evaluated, CRP was the one most frequently studied. The SROC presented an area under the curve = 0.77 (CI: 0.73-0.81), which indicates good accuracy to distinguish bacterial from nonbacterial infections. However, the optimal cutoff of CRP could not be assessed, and we found insufficient evidence about its impact on antibiotic prescription and clinical outcome. The role of CRP and other host biomarker POCTs for the assessment of acute non-malarial febrile illnesses in resource-constraint settings deserves further studies.

Evaluation of C-reactive protein and myxovirus resistance protein A to guide the rational use of antibiotics among acute febrile adult patients in Northwest Ethiopia

OBJECTIVES

In low-resource settings, treatment is often given empirically without knowledge of the aetiology due to a lack of diagnostics. In the search for reliable rapid tests to guide treatment work-up, this study was performed to determine whether two biomarkers could differentiate bacterial from non-bacterial infections in acute febrile patients.

METHODS

Adults with acute fever were recruited at a referral hospital in Ethiopia. The QuikRead Go test was used to quantify C-reactive protein (qCRP) and the FebriDx test was used for combined qualitative detection of the bacterial CRP marker with myxovirus resistance protein A (MxA), a viral biomarker.

RESULTS

Of the 200 patients included in this study, most presented with 2-3 days of fever, headache, and joint pain. Antibiotics were prescribed for 83.5% and antimalarials for 36.5%, while a bacterial infection was only confirmed in 5% and malaria in 11%. The median qCRP level for confirmed bacterial infections was 128 mg/l. The FebriDx and QuikRead Go test had an overall agreement of 72.0%.

CONCLUSIONS

An over-prescription of antibiotics for febrile patients was observed, even for those with low CRP levels and without a confirmed bacterial infection. The added value of the FebriDx was limited, while the combined use of rapid tests for qCRP and malaria should be considered for the management of acute febrile illness and antibiotic stewardship.

Point-of-Care Biomarkers to Guide Antibiotic Prescription for Acute Febrile Illness in Sub-Saharan Africa: Promises and Caveats

Empiric malaria treatment in Sub-Saharan Africa has significantly decreased with the scaling-up of malaria rapid diagnostic tests; this coincided with a pronounced increase in empiric antibiotic prescriptions. In high-income countries, guidance for antibiotic prescriptions using biomarkers such as C-reactive protein (CRP) and procalcitonin (PCT) has reduced antibiotic use while safe-guarding patient safety. Importantly, several low-cost point-of-care CRP/PCT tests are currently available. However, only a few studies on the role of CRP/PCT in differentiating bacterial vs viral infections in acute febrile illness have been conducted in Sub-Saharan Africa. Studies from Central and West Africa (most of which is malaria-endemic) are particularly scarce, and only 1 has included adults. The evidence base for point-of-care use of CRP/PCT biomarkers in acute fever in Sub-Saharan Africa should be urgently built. Before engaging in clinical trials to assess clinical impact, pilot studies should be conducted to address key knowledge gaps including recommended CRP/PCT cutoff values and the effect of malaria coinfection.

Previously Derived Host Gene Expression Classifiers Identify Bacterial and Viral Etiologies of Acute Febrile Respiratory Illness in a South Asian Population

Background

Pathogen-based diagnostics for acute respiratory infection (ARI) have limited ability to detect etiology of illness. We previously showed that peripheral blood-based host gene expression classifiers accurately identify bacterial and viral ARI in cohorts of European and African descent. We determined classifier performance in a South Asian cohort.

Methods

Patients ≥15 years with fever and respiratory symptoms were enrolled in Sri Lanka. Comprehensive pathogen-based testing was performed. Peripheral blood ribonucleic acid was sequenced and previously developed signatures were applied: a pan-viral classifier (viral vs nonviral) and an ARI classifier (bacterial vs viral vs noninfectious).

Results

Ribonucleic acid sequencing was performed in 79 subjects: 58 viral infections (36 influenza, 22 dengue) and 21 bacterial infections (10 leptospirosis, 11 scrub typhus). The pan-viral classifier had an overall classification accuracy of 95%. The ARI classifier had an overall classification accuracy of 94%, with sensitivity and specificity of 91% and 95%, respectively, for bacterial infection. The sensitivity and specificity of C-reactive protein (>10 mg/L) and procalcitonin (>0.25 ng/mL) for bacterial infection were 100% and 34%, and 100% and 41%, respectively.

Conclusions

Previously derived gene expression classifiers had high predictive accuracy at distinguishing viral and bacterial infection in South Asian patients with ARI caused by typical and atypical pathogens.

Causes of fever in primary care in Southeast Asia and the performance of C-reactive protein in discriminating bacterial from viral pathogens

OBJECTIVES

This study investigated causes of fever in the primary levels of care in Southeast Asia, and evaluated whether C-reactive protein (CRP) could distinguish bacterial from viral pathogens.

METHODS

Blood and nasopharyngeal swab specimens were taken from children and adults with fever (>37.5 °C) or history of fever (<14 days) in Thailand and Myanmar.

RESULTS

Of 773 patients with at least one blood or nasopharyngeal swab specimen collected, 227 (29.4%) had a target organism detected. Influenza virus type A was detected in 85/227 cases (37.5%), followed by dengue virus (30 cases, 13.2%), respiratory syncytial virus (24 cases, 10.6%) and Leptospira spp. (nine cases, 4.0%). Clinical outcomes were similar between patients with a bacterial or a viral organism, regardless of antibiotic prescription. CRP was higher among patients with a bacterial organism compared with those with a viral organism (median 18 mg/L, interquartile range [10-49] versus 10 mg/L [≤8-22], p = 0.003), with an area under the curve of 0.65 (95% CI 0.55-0.75).

CONCLUSIONS

Serious bacterial infections requiring antibiotics are an exception rather than the rule in the first line of care. CRP testing could assist in ruling out such cases in settings where diagnostic uncertainty is high and routine antibiotic prescription is common. The original CRP randomised controlled trial was registered with ClinicalTrials.gov, number NCT02758821.

Clinical Characteristics and Outcome of Children Hospitalized With Scrub Typhus in an Area of Endemicity

BACKGROUND

Scrub typhus, caused by Orientia tsutsugamushi, is a major cause of acute febrile illness in children in the rural tropics.

METHODS

We recruited 60 febrile pediatric patients with a positive scrub typhus rapid diagnostic test result and 40 healthy controls from Chiang Rai Province in northern Thailand. Diagnosis was confirmed by the detection of (1) O. tsutsugamushi-specific DNA in blood or eschar samples with a polymerase chain reaction assay, (2) a fourfold rise in immunoglobulin M (IgM) titer to ≥1:3200 in paired plasma samples with an indirect immunofluorescence assay (IFA), or (3) a single IgM titer of ≥1:3200 in an acute plasma sample with an IFA. Demographic, clinical, and laboratory data were collected, and patients were followed up for 1 year.

RESULTS

Diagnosis was confirmed in 35 (58%) of 60 patients, and all controls tested negative for scrub typhus. Patients with confirmed scrub typhus had clinical symptoms, including fever (35 of 35 [100%]), eschar (21 of 35 [60%]), cough (21 of 35 [60%]), tachypnea (16 of 35 [46%]), lymphadenopathy (15 of 35 [43%]), and headache (14 of 35 [40%]). Only 4 (11%) of 35 patients received appropriate antibiotic treatment for scrub typhus before admission. The median fever-clearance time was 36 hours (interquartile range, 24-53 hours). Complications observed include hepatitis (9 of 35 [26%]), severe thrombocytopenia (7 of 35 [20%]), pneumonitis (5 of 35 [14%]), circulatory shock (4 of 35 [11%]), and acute respiratory distress syndrome (3 of 35 [9%]). Treatment failure, defined by failure to defervesce within 72 hours of antibiotic treatment initiation, was noted in 8 (23%) of 35 patients, and 1 (3%) of the 35 patients died. No evidence of relapse or reinfection was found.

CONCLUSION

Pediatric scrub typhus in northern Thailand is often severe and potentially fatal with delays in treatment a likely contributing factor. Additional studies to investigate the bacterial, pharmacologic, and immunologic factors related to treatment outcome along with measures to improve public awareness should be prioritized.

Spotted Fever Group Rickettsia Infection of Cats and Cat Fleas in Northeast Thailand

Rickettsia species cause rickettsioses, which are zoonotic diseases found worldwide, and are transmitted by arthropods such as lice, fleas, ticks, and mites. In Thailand, flea infestations are common among cats and dogs. This study aimed at determining the exposure to spotted fever group rickettsiae (SFGR) of cats in surrounding areas of Rajabhat Maha Sarakham University, Muang district, Maha Sarakham province and rickettsial infection among cat fleas, Ctenocephalides felis, collected from dogs of the surrounding area of Waeng Noi district, Khon Kaen province. Forty-two cat sera were assessed for IgG antibody titers against SFGR by a group-specific enzyme-linked immunosorbent assay. The prevalence of seroreactive cats was 4.76% (2/42). DNA preparations from 23 individual cat fleas from three dogs were assessed by Rickettsia genus-specific, group-specific, and species-specific quantitative real-time PCR (qPCR) assays. Positive results were confirmed by ompB gene fragment sequencing. Twenty-one of 23 cat fleas were positive for Rickettsia asembonensis, and the other two DNA preparations were negative for rickettsial DNA. This study's finding indicates that companion cats and dogs in Northeast Thailand are exposed to SFGR and that exposure may be due to infection with R. asembonensis, an organism known to infect humans, monkeys, and dogs. Clinicians for humans and animals in Northeast Thailand should be aware of rickettsial infections among their patients.

The estimated burden of scrub typhus in Thailand from national surveillance data (2003-2018)

BACKGROUND

Scrub typhus is a major cause of acute febrile illness in the tropics and is endemic over large areas of the Asia Pacific region. The national and global burden of scrub typhus remains unclear due to limited data and difficulties surrounding diagnosis.

METHODOLOGY/PRINCIPAL FINDINGS

Scrub typhus reporting data from 2003-2018 were collected from the Thai national disease surveillance system. Additional information including the district, sub-district and village of residence, population, geographical, meteorological and satellite imagery data were also collected for Chiangrai, the province with the highest number of reported cases from 2003-2018. From 2003-2018, 103,345 cases of scrub typhus were reported with the number of reported cases increasing substantially over the observed period. There were more men than women, with agricultural workers the main occupational group affected. The majority of cases occurred in the 15-64 year old age group (72,144/99,543, 72%). Disease burden was greatest in the northern region, accounting for 53% of the total reported cases per year (mean). In the northern region, five provinces-Chiangrai, Chiangmai, Tak, Nan and Mae Hong Son-accounted for 84% (46,927/55,872) of the total cases from the northern region or 45% (46,927/103,345) of cases nationally. The majority of cases occurred from June to November but seasonality was less marked in the southern region. In Chiangrai province, elevation, rainfall, temperature, population size, habitat complexity and diversity of land cover contributed to scrub typhus incidence.

INTERPRETATION

The burden of scrub typhus in Thailand is high with disease incidence rising significantly over the last two decades. However, disease burden is not uniform with northern provinces particularly affected. Agricultural activity along with geographical, meteorological and land cover factors are likely to contribute to disease incidence. Our report, along with existing epidemiological data, suggests that scrub typhus is the most clinically important rickettsial disease globally.

C-reactive protein as a potential biomarker for disease progression in dengue: a multi-country observational study

BACKGROUND

Dengue infection can cause a wide spectrum of clinical outcomes. The severe clinical manifestations occur sufficiently late in the disease course, during day 4-6 of illness, to allow a window of opportunity for risk stratification. Markers of inflammation may be useful biomarkers. We investigated the value of C-reactive protein (CRP) measured early on illness days 1-3 to predict dengue disease outcome and the difference in CRP levels between dengue and other febrile illnesses (OFI).

METHOD

We performed a nested case-control study using the clinical data and samples collected from the IDAMS-consortium multi-country study. This was a prospective multi-center observational study that enrolled almost 8000 participants presenting with a dengue-like illness to outpatient facilities in 8 countries across Asia and Latin America. Predefined severity definitions of severe and intermediate dengue were used as the primary outcomes. A total of 281 cases with severe/intermediate dengue were compared to 836 uncomplicated dengue patients as controls (ratio 1:3), and also 394 patients with OFI.

RESULTS

In patients with confirmed dengue, median (interquartile range) of CRP level within the first 3 days was 30.2 mg/L (12.4-61.2 mg/L) (uncomplicated dengue, 28.6 (10.5-58.9); severe or intermediate dengue, 34.0 (17.4-71.8)). Higher CRP levels in the first 3 days of illness were associated with a higher risk of severe or intermediate outcome (OR 1.17, 95% CI 1.07-1.29), especially in children. Higher CRP levels, exceeding 30 mg/L, also associated with hospitalization (OR 1.37, 95% CI 1.14-1.64) and longer fever clearance time (HR 0.84, 95% CI 0.76-0.93), especially in adults. CRP levels in patients with dengue were higher than patients with potential viral infection but lower than patients with potential bacterial infection, resulting in a quadratic association between dengue diagnosis and CRP, with levels of approximately 30 mg/L associated with the highest risk of having dengue. CRP had a positive correlation with total white cell count and neutrophils and negative correlation with lymphocytes, but did not correlate with liver transaminases, albumin, or platelet nadir.

CONCLUSIONS

In summary, CRP measured in the first 3 days of illness could be a useful biomarker for early dengue risk prediction and may assist differentiating dengue from other febrile illnesses.

Determination of Optimal Diagnostic Cut-Offs for the Naval Medical Research Center Scrub Typhus IgM ELISA in Chiang Rai, Thailand

In this diagnostic accuracy study, we evaluated data from 135 febrile patients from Chiang Rai, to determine the optimal optical density (OD) cutoffs for an in-house scrub typhus IgM ELISA. Receiver operating characteristic curves were generated using a panel of reference assays, including an IgM immunofluorescence assay (IFA), PCR, in vitro isolation, presence of an eschar, or a combination of these. Altogether, 33 patients (24.4%) were diagnosed as having scrub typhus. Correlation between positivity by IFA and increasing OD values peaked at a cutoff of 2.0, whereas there was little association between positivity by culture or eschar with increasing ELISA cutoffs—cutoffs of 3.0 and 4.0 were demonstrated to be optimal for the total absorbance of the OD at dilutions 1:100, 1:400, 1:1,600, and 1:6,400, for admission and convalescent samples, respectively. The optimal cutoff at a 1:100 dilution was found to be between 1.85 and 2.22 for admission samples and convalescent-phase samples, respectively. Sensitivities for the cutoffs varied from 57.1% to 90.0% depending on the reference test and sample timing, whereas specificities ranged from 85.2% to 99.0%. We therefore recommend a cutoff of around 2.0, depending on the sensitivity and specificity desired in clinical or epidemiological settings. The results demonstrate the ELISA to be a valuable diagnostic tool, suitable for use in resource-limited endemic regions, especially when used in combination with other diagnostic modalities such as the presence of an eschar.

When and what to test for: A cost-effectiveness analysis of febrile illness test-and-treat strategies in the era of responsible antibiotic use

BACKGROUND

Febrile illness caused by viral and bacterial diseases (e.g., dengue and leptospirosis) often have similar symptoms and are difficult to differentiate without diagnostic tests. If not treated appropriately, patients may experience serious complications. The question of what diagnostic tests to make available to providers in order to inform antibiotic therapy remains an open problem for health services facing limited resources.

METHODS AND FINDINGS

We formulated the problem of minimizing the weighted average of antibiotic underuse and overuse to inform the optimal diagnostic test and antibiotic treatment options for given occurrence probabilities of several bacterial and viral infections. We modeled the weight of antibiotic overuse as a monetary penalty per unnecessarily administered course, which we varied in both the base case and sensitivity analysis. Detailed Markov cohort models of febrile illness progression were used to estimate the weight of antibiotic underuse. The model accounted for multiple infections simultaneously and incorporated test, treatment, and other direct and indirect costs, as well as the effect of delays in seeking care and test turnaround times. We used the Markov models to numerically estimate disability-adjusted life years (DALYs), pre-penalty costs, and likelihood of antibiotics overuse per patient for fifteen different strategies in two example settings in Thailand, one with a higher probability of bacterial infections (Northern Thailand, Scenario A) and one with a higher probability of viral infections (Bangkok, Scenario B). We found that empirical antibiotic treatment to all patients always incurs the lowest pre-penalty cost (Scenario A: $47.5/patient, $100.6/patient, $149.5/patient for patients seeking care on day one, day four, and day ten respectively; Scenario B: $94.1/patient, $108.7/patient, $122.1/patient on day one, day four, and day ten respectively), and the lowest DALYs, (Scenario A: 0.2 DALYs/patient, 0.9 DALYs/patient, 1.7 DALYs/patient on day one, day four, and day ten, respectively; Scenario B: 0.5 DALYs/patient, 0.7 DALYs/patient, 0.9 DALYs/patient on day one, day four, and day ten, respectively). However, such strategy resulted in the highest proportion of antibiotic overuse per patient (Scenario A: 38.1%, 19.3%, 7.5% on day one, day four, and day ten, respectively; Scenario B: 82.9%, 42.1%, 16.3% on day one, day four, and day ten, respectively). Consequently, empirical antibiotic treatment became suboptimal with antibiotic overuse penalties above $12,800/course, $18,400/course, $23,900/course for patients presenting on day one, day four, and day ten in Scenario A and above $1,100/course, $1,500/course, $1,600/course for patients presenting on day one, day four, and day ten in Scenario B.

CONCLUSIONS

Empirical antibiotic treatment to all patients provided the best outcomes if antibiotic overuse was not the primary concern or if presenting with viral disease (such as dengue) was unlikely. Empirical antibiotic treatment to severe patients only was in most cases not beneficial. Otherwise, strategies involving diagnostic tests became optimal. In particular, our results indicated that single test strategies (bacterial RDT or viral PCR) were optimal in regions with a greater probability of presenting with viral infection. PCR-led strategies (e.g., parallel bacterial PCR, or multiplex PCR) are robust under parameter uncertainty (e.g., with uncertain disease occurrence probabilities).

Sensitivity of C-reactive protein for the identification of patients with laboratory-confirmed bacterial infections in northern Tanzania

OBJECTIVE

Identifying febrile patients requiring antibacterial treatment is challenging, particularly in low-resource settings. In South-East Asia, C-reactive protein (CRP) has been demonstrated to be highly sensitive and moderately specific in detecting bacterial infections and to safely reduce unnecessary antibacterial prescriptions in primary care. As evidence is scant in sub-Saharan Africa, we assessed the sensitivity of CRP in identifying serious bacterial infections in Tanzania.

METHODS

Samples were obtained from inpatients and outpatients in a prospective febrile illness study at two hospitals in Moshi, Tanzania, 2011-2014. Bacterial bloodstream infections (BSI) were established by blood culture, and bacterial zoonotic infections were defined by ≥4 fold rise in antibody titre between acute and convalescent sera. The sensitivity of CRP in identifying bacterial infections was estimated using thresholds of 10, 20 and 40 mg/l. Specificity was not assessed because determining false-positive CRP results was limited by the lack of diagnostic testing to confirm non-bacterial aetiologies and because ascertaining true-negative cases was limited by the imperfect sensitivity of the diagnostic tests used to identify bacterial infections.

RESULTS

Among 235 febrile outpatients and 569 febrile inpatients evaluated, 31 (3.9%) had a bacterial BSI and 61 (7.6%) had a bacterial zoonosis. Median (interquartile range) CRP values were 173 (80-315) mg/l in bacterial BSI, and 108 (31-208) mg/l in bacterial zoonoses. The sensitivity (95% confidence intervals) of CRP was 97% (83%-99%), 94% (79%-98%) and 90% (74%-97%) for identifying bacterial BSI, and 87% (76%-93%), 82% (71%-90%) and 72% (60%-82%) for bacterial zoonoses, using thresholds of 10, 20 and 40 mg/l, respectively.

CONCLUSION

C-reactive protein was moderately sensitive for bacterial zoonoses and highly sensitive for identifying BSIs. Based on these results, operational studies are warranted to assess the safety and clinical utility of CRP for the management of non-malaria febrile illness at first-level health facilities in sub-Saharan Africa.

Potential usefulness of C-reactive protein and procalcitonin determination in patients admitted for neurological disorders in rural Democratic Republic of Congo

In low-resource hospitals of central Africa, neurological disorders are frequent and etiologies very diverse. The difficulty to identify invasive bacterial infections in this setting results in major antibiotic overuse. Biomarkers such as C-reactive protein (CRP) and procalcitonin (PCT) may help discriminate these conditions. We retrospectively determined the concentrations of CRP and PCT in the sera of patients consecutively enrolled from 2012 to 2015 in an etiological study on neurological disorders at the rural hospital of Mosango, Democratic Republic of Congo. Invasive bacterial infection had been diagnosed by the demonstration of a bacterial pathogen in cerebrospinal fluid or blood cultures or the presence of radiological pneumonia. Sera of 313 (89.2%) and 317 (90.3%) of the 351 enrolled participants were available for determination of CRP and PCT concentrations respectively. Areas under the receiver operating characteristic curves for invasive bacterial infection, diagnosed in 19 tested cases, were 94.3% for CRP and 91.7% for PCT. No single case had a normal CRP concentration (<10 mg/L). Our data, although limited, suggest that CRP or PCT concentrations may help discriminate invasive bacterial infections in patients with neurological disorders in tropical settings and that normal CRP values could assist in withholding antibiotics.

Accounting for aetiology: can regional surveillance data alongside host biomarker-guided antibiotic therapy improve treatment of febrile illness in remote settings?

Background: Across Southeast Asia, declining malaria incidence poses a challenge for healthcare providers, in how best to manage the vast majority of patients with febrile illnesses who have a negative malaria test. In rural regions, where the majority of the population reside, empirical treatment guidelines derived from central urban hospitals are often of limited relevance. In these settings, health workers with limited training deliver care, often without any laboratory diagnostic support. In this paper, we model the impact of point-of-care C-reactive protein testing to inform the decision to prescribe antibiotics and regional surveillance data to inform antibiotic selection, and then simulate the subsequent impact on mortality from febrile illnesses, rooted in the real-world context of rural Savannakhet province, southern Laos. Methods: Our model simulates 100 scenarios with varying quarterly incidence of six key pathogens known to be prevalent in rural Laos. In the simulations, community health workers either prescribe antibiotics in-line with current practice as documented in health facilities in rural Laos, or with the aid of the two interventions. We provide cost-effectiveness estimates for each strategy alone and then for an integrated approach using both interventions. Results: We find that each strategy is predicted to be highly cost-effective, and that the combined approach is predicted to result in the biggest reduction in mortality (averting a predicted 510 deaths per year in rural Savannakhet, a 28% reduction compared to standard practice) and is highly cost-effective, with an incremental cost-effectiveness ratio of just $66 per disability-adjusted life year averted. Conclusions: Substantial seasonal variation in the predicted optimal empirical antibiotic treatment for febrile illness highlights the benefits of up-to-date information on regional causes of fever. In this modelling analysis, an integrated system incorporating point-of-care host biomarker testing and regional surveillance data appears highly cost-effective, and may warrant piloting in a real-life setting.

Usefulness of C-Reactive Protein in Differentiating Acute Leptospirosis and Dengue Fever in French Guiana

Objective

Leptospirosis and dengue fever (DF) are hard-to-differentiate diseases in cocirculating areas, especially during DF epidemics. Misdiagnosis and ensuing lack of antibiotic therapy can be detrimental in leptospirosis. The objective of this study was to identify factors that help differentiate acute leptospirosis from dengue fever on admission.

Method

Patients with leptospirosis (positive serology or polymerase chain reaction) were compared with patients with DF (positive nonstructural 1 [NS1] antigen) in a case-control study with age matching. Data on admission were compared using bivariate analysis and multivariate analysis.

Results

Seventy-two patients with leptospirosis were compared to 216 patients with DF. In bivariate analysis, the factors associated with leptospirosis were male gender, cough, anemia, and elevated blood levels of C-reactive protein (CRP), leukocytes, creatinine, bilirubin, and creatine phosphokinase. Exanthema, purpura, myalgia, headache, and neutropenia were associated with DF. In multivariate analysis, elevated blood levels of leukocytes, bilirubin, and CRP were associated with leptospirosis. The CRP threshold of 50 mg/L taken alone had elevated sensitivity and specificity.

Conclusions

The CRP level, an easy-to-obtain biomarker, was a powerful tool to differentiate on admission leptospirosis and DF. Facing a dengue-like syndrome in cocirculating areas and awaiting new specific rapid diagnostic tests, CRP dosing could help the clinician to promptly consider the diagnosis of leptospirosis and initiate antibiotic therapy early.

Diversity of infectious aetiologies of acute undifferentiated febrile illnesses in south and Southeast Asia: a systematic review

BACKGROUND

Acute undifferentiated febrile illness (AUFI) is caused by a multitude of diverse pathogens, with significant morbidity and mortality in the developing world. The objective of this review was to characterise the diversity and relative importance of common infectious aetiologies of AUFI in South and Southeast Asia.

METHODS

We conducted a comprehensive literature review to identify common aetiologies of AUFI in Asian countries. Four medical and life sciences databases including PubMed, Medline, Embase and Cochrane Central, and Google Scholar were searched for articles published from January 1998 to March 2019.

RESULTS

Forty-three studies met the inclusion criteria. Among AUFI cases, viral aetiologies at 18.5% (14888) were more common than bacterial aetiologies (12.9% [10384]). From 80,554 cases, dengue fever was the most common aetiology (11.8%, 9511), followed by leptospirosis (4.4%, 3549), typhoid (4.0%, 3258), scrub typhus (4.0%, 3243) and influenza other than H1N1 (3.1%, 2514). In both adults and children: dengue fever was the leading cause of AUFI with 16.6% (1928) and 18.7% (1281) of the total cases. In admitted patients, dengue fever was the main cause of AUFI at 16.4% (2377), however leptospirosis at 13.9% (2090) was the main cause of AUFI for outpatients. In South Asia, dengue fever was the main cause of AUFI, causing 12.0% (6821) of cases, whereas in Southeast Asia, leptospirosis was the main diagnosis, causing 12.1% (2861) of cases.

CONCLUSIONS

In this study the most common causes of AUFI were viral, followed by bacterial and protozoal (malaria) infections. Dengue was the commonest virus that caused AUFI while leptospirosis and typhoid were important bacterial infectious causes. Therefore, it is imperative to maintain a sound epidemiological knowledge of AUFI so that evidence-based diagnostic criteria and treatment guidelines can be developed.

Molecular epidemiology of Leptospira interrogans in Rattus norvegicus in Hanoi, Vietnam

Leptospirosis is a zoonotic disease that is caused by pathogenic spirochaetes of Leptospira spp. and it has become a public health concern in urban localities in the tropics. Rats are important reservoir animals for the transmission of leptospirosis in urban areas. Leptospirosis is considered endemic in Vietnam. However, information on the causative Leptospira genotypes and serotypes in the country is limited. We investigated the carrier status of Leptospira spp. in rats captured in Hanoi by culturing and DNA detection. Isolates were characterized using a serological method and multiple-locus variable-number tandem repeat analysis (MLVA). We captured 144 rats (1 Rattus argentiventer, 135 R. norvegicus, and 8 R. rattus) and obtained 17 L. interrogans, determined by rrs sequencing, from R. norvegicus (12.6%). Sixteen of the isolates were serogroup Bataviae. Five of the 16 isolates exhibited an MLVA type identical to that of the serovar Bataviae reference strain Van Tienen, while there were nine repeats for the other 11 isolates at VNTR31 compared with the reference strain. The remaining isolate grew poorly, and we were unable to determine its serogroup. However, it had an MLVA type matching those of serogroup Pomona strains isolated from R. norvegicus in Japan. Three different flaB sequences were detected in 23 out of 81 R. norvegicus kidney tissue samples (28.4%) using nested PCR followed by DNA sequencing. Two of the sequences were identical with those of serogroups Bataviae and Pomona, and no strain with another sequence was detected in the present study. The present study reveals a high prevalence rate of L. interrogans among R. norvegicus in Hanoi, Vietnam, indicating a potential risk of rat-borne leptospirosis in the area. The present study also demonstrates that a fastidious L. interrogans strain circulates among rats and that molecular detection is crucial in facilitating the accurate determination of reservoir animals.

A novel diagnostic algorithm equipped on an automated hematology analyzer to differentiate between common causes of febrile illness in Southeast Asia

BACKGROUND

Distinguishing arboviral infections from bacterial causes of febrile illness is of great importance for clinical management. The Infection Manager System (IMS) is a novel diagnostic algorithm equipped on a Sysmex hematology analyzer that evaluates the host response using novel techniques that quantify cellular activation and cell membrane composition. The aim of this study was to train and validate the IMS to differentiate between arboviral and common bacterial infections in Southeast Asia and compare its performance against C-reactive protein (CRP) and procalcitonin (PCT).

METHODOLOGY/PRINCIPAL FINDINGS

600 adult Indonesian patients with acute febrile illness were enrolled in a prospective cohort study and analyzed using a structured diagnostic protocol. The IMS was first trained on the first 200 patients and subsequently validated using the complete cohort. A definite infectious etiology could be determined in 190 of 463 evaluable patients (41%), including 89 arboviral infections (81 dengue and 8 chikungunya), 94 bacterial infections (26 murine typhus, 16 salmonellosis, 6 leptospirosis and 46 cosmopolitan bacterial infections), 3 concomitant arboviral-bacterial infections, and 4 malaria infections. The IMS detected inflammation in all but two participants. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the IMS for arboviral infections were 69.7%, 97.9%, 96.9%, and 77.3%, respectively, and for bacterial infections 77.7%, 93.3%, 92.4%, and 79.8%. Inflammation remained unclassified in 19.1% and 22.5% of patients with a proven bacterial or arboviral infection. When cases of unclassified inflammation were grouped in the bacterial etiology group, the NPV for bacterial infection was 95.5%. IMS performed comparable to CRP and outperformed PCT in this cohort.

CONCLUSIONS/SIGNIFICANCE

The IMS is an automated, easy to use, novel diagnostic tool that allows rapid differentiation between common causes of febrile illness in Southeast Asia.

Epidemiology, Risk Factors and Seasonal Variation of Scrub Typhus Fever in Central Nepal

Scrub typhus is a mite-borne acute febrile illness caused by Orientia. tsutsugamushi, a zoonotic bacterial infection common in the region known as the tsutsugamushi triangle. This study aims to determine the seroprevalence, seasonal variation, and risk factors of scrub typhus among the acute febrile illness patients attending different hospitals of central Nepal. Blood samples were collected from hospitalized patients of acute febrile illness suspected of scrub typhus infection attending different hospitals of central Nepal from April 2017 to March 2018. The IgM antibody to Orientia tsutsugamushi was detected by using the Scrub Typhus Detect™ Kit. Among the total cases (1585), 358 (22.58%) were positive for IgM Antibodies. Multivariate analysis identified several risks factors to be significantly associated with the scrub typhus infection, including gender (female) (odds ratio [OR] = 1.976, p ≤ 0.001, confidence interval [CI] = 1.417–2.756), rural residential location (odds ratio [OR] = 0.431, p = 0.001, confidence interval [CI] = 0.260–0.715), house near grassland (odds ratio [OR] = 3.288, p ≤ 0.001, confidence interval [CI] = 1.935–5.587), and working in the field (odds ratio [OR] = 9.764, p = 0.004, confidence interval [CI] = 2.059–46.315). The study findings indicate scrub typhus infection to be a significant health problem in Nepal. The proper diagnosis of infection cases, timely institution of therapy, public awareness, and vector control are important measures to be taken for the prevention and management of scrub typhus.

The validity of diagnostic cut-offs for commercial and in-house scrub typhus IgM and IgG ELISAs: A review of the evidence

BACKGROUND

Scrub typhus is a neglected tropical disease that causes acute febrile illness. Diagnosis is made based upon serology, or detection of the causative agent-Orientia tsutsugamushi-using PCR or in vitro isolation. The enzyme-linked immunosorbent assay (ELISA) is an objective and reproducible means of detecting IgM or IgG antibodies. However, lack of standardization in ELISA methodology, as well as in the choice of reference test with which the ELISA is compared, calls into question the validity of cut-offs used in diagnostic accuracy studies and observational studies.

METHODOLOGY/PRINCIPAL FINDINGS

A PubMed search and manual screening of reference lists identified 46 studies that used ELISA antibody cut-offs to diagnose scrub typhus patients, 22 of which were diagnostic accuracy studies. Overall, 22 studies (47.8%) provided little to no explanation as to how the ELISA cut-off was derived, and 7 studies (15.2%) did not even state the cut-off used. Variation was seen locally in reference standards used, in terms of both the diagnostic test and cut-off titer. Furthermore, with the exception of studies using ELISAs manufactured by InBios, there was no standardization of the selection of antigenic strains. As a result, no consensus was found for determining a cut-off, ELISA methodology, or for a single value diagnostic cut-off.

CONCLUSIONS/SIGNIFICANCE

We have concluded that there is a lack of consensus in the determination of a cut-off. We recommend interpreting the results from these studies with caution. Further studies will need to be performed at each geographic location to determine region-specific cut-offs, taking into consideration background antibody levels to discriminate true disease from healthy individuals.