Twelve years of dengue surveillance in Belgian travellers and significant increases in the number of cases in 2010 and 2013

From a long-distance threat to the invasion front: a review of the invasive Aedes mosquito species in Belgium between 2007 and 2020

Invasive mosquito species (IMS) and their associated mosquito-borne diseases are emerging in Europe. In Belgium, the first detection of Aedes albopictus (Skuse 1894) occurred in 2000 and of Aedes japonicus japonicus (Theobald 1901) in 2002. Early detection and control of these IMS at points of entry (PoEs) are of paramount importance to slow down any possible establishment. This article reviews the introductions and establishments recorded of three IMS in Belgium based on published (2007-2014) and unpublished (2015-2020) data collected during several surveillance projects. In total, 52 PoEs were monitored at least once for the presence of IMS between 2007 and 2020. These included used tyre and lucky bamboo import companies, airports, ports, parking lots along highways, shelters for imported cutting plants, wholesale markets, industrial areas, recycling areas, cemeteries and an allotment garden at the country border with colonised areas. In general, monitoring was performed between April and November. Mosquitoes were captured with adult and oviposition traps as well as by larval sampling. Aedes albopictus was detected at ten PoEs, Ae. japonicus at three PoEs and Aedes koreicus (Edwards 1917) at two PoEs. The latter two species have established overwintering populations. The percentage of PoEs positive for Ae. albopictus increased significantly over years. Aedes albopictus is currently entering Belgium through lucky bamboo and used tyre trade and passive ground transport, while Ae. japonicus through used tyre trade and probably passive ground transport. In Belgium, the import through passive ground transport was first recorded in 2018 and its importance seems to be growing. Belgium is currently at the invasion front of Ae. albopictus and Ae. japonicus. The surveillance and control management actions at well-known PoEs associated to long-distance introductions are more straightforward than at less-defined PoEs associated with short-distance introductions from colonised areas. These latter PoEs represent a new challenge for IMS management in Belgium in the coming years. Aedes albopictus is expected to become established in Belgium in the coming years, hence increasing the likelihood of local arbovirus transmission. The implementation of a sustainable, structured and long-term IMS management programme, integrating active and passive entomological surveillance, vector control and Public Health surveillance is therefore pivotal.

Peptide Biomarkers for the Diagnosis of Dengue Infection

In a world with an increasing population at risk of exposure to arthropod-borne flaviviruses, access to timely and accurate diagnostic tests would impact profoundly on the management of cases. Twenty peptides previously identified using a flavivirus proteome-wide microarray were evaluated to determine their discriminatory potential to detect dengue virus (DENV) infection. This included nine peptides recognized by IgM antibodies (PM peptides) and 11 peptides recognized by IgG antibodies (PG peptides). A bead-based multiplex peptide immunoassay (MPIA) using the Luminex technology was set-up to determine Ab binding levels to each of these peptides in a panel of 323 carefully selected human serum samples. Sera are derived from individuals either infected with different viruses, namely, the four DENV serotypes, Zika virus (ZIKV), yellow fever virus (YFV), chikungunya virus (CHIKV), West Nile virus (WNV) and Human immunodeficiency virus (HIV), or receiving vaccination against YFV, tick-borne encephalitis (TBEV), and Japanese encephalitis virus (JEV). Additionally, a set of healthy controls were included. We targeted a minimum specificity of 80% for all the analysis. The PG-9 peptide had the best sensitivity (73%) when testing DENV sera from acute patients (A-DENV; <8 days since symptom onset). With sera from convalescent DENV patients (C-DENV; >10 days since symptom onset) the FPG-1 peptide was the best seromarker with a sensitivity of 86%. When combining all A-DENV and C-DENV samples, peptides PM-22 and FPG-1 had the best-diagnostic performance with a sensitivity of 60 and 61.1%, and areas under the curve (AUC) of 0.7865 and 0.8131, respectively. A Random forest (RF) algorithm was used to select the best combination of peptides to classify DENV infection at a targeted specificity >80%. The best RF model for PM peptides that included A-DENV and C-DENV samples, reached a sensitivity of 72.3%, while for PG peptides, the best RF models for A-DENV only, C-DENV only and A-DENV + C-DENV reached a sensitivity of 88.9%, 89.1%, and 88.3%, respectively. In conclusion, the combination of multiple peptides constitutes a founding set of seromarkers for the discrimination of DENV infected individuals from other flavivirus infections.

Uncovering the Burden of Dengue in Africa: Considerations on Magnitude, Misdiagnosis, and Ancestry

Dengue is a re-emerging neglected disease of major public health importance. This review highlights important considerations for dengue disease in Africa, including epidemiology and underestimation of disease burden in African countries, issues with malaria misdiagnosis and co-infections, and potential evidence of genetic protection from severe dengue disease in populations of African descent. The findings indicate that dengue virus prevalence in African countries and populations may be more widespread than reported data suggests, and that the Aedes mosquito vectors appear to be increasing in dissemination and number. Changes in climate, population, and plastic pollution are expected to worsen the dengue situation in Africa. Dengue misdiagnosis is also a problem in Africa, especially due to the typical non-specific clinical presentation of dengue leading to misdiagnosis as malaria. Finally, research suggests that a protective genetic component against severe dengue exists in African descent populations, but further studies should be conducted to strengthen this association in various populations, taking into consideration socioeconomic factors that may contribute to these findings. The main takeaway is that Africa should not be overlooked when it comes to dengue, and more attention and resources should be devoted to this disease in Africa.

COVID-19 Antibody Detecting Rapid Diagnostic Tests Show High Cross-Reactivity When Challenged with Pre-Pandemic Malaria, Schistosomiasis and Dengue Samples

COVID-19 Antibody Detecting Rapid Diagnostic Tests (COVID-19 Ab RDTs) are the preferred tool for SARS-CoV-2 seroprevalence studies, particularly in low- and middle-income countries. The present study challenged COVID-19 Ab RDTs with pre-pandemic samples of patients exposed to tropical pathogens. A retrospective study was performed on archived serum (n = 94) and EDTA whole blood (n = 126) samples obtained during 2010–2018 from 196 travelers with malaria (n = 170), schistosomiasis (n = 25) and dengue (n = 25). COVID-19 Ab RDTs were selected based on regulatory approval status, independent evaluation results and detecting antigens. Among 13 COVID-19 Ab RDT products, overall cross-reactivity was 18.5%; cross-reactivity for malaria, schistosomiasis and dengue was 20.3%, 18.1% and 7.5%, respectively. Cross-reactivity for current and recent malaria, malaria antibodies, Plasmodium species and parasite densities was similar. Cross-reactivity among the different RDT products ranged from 2.7% to 48.9% (median value 14.5%). IgM represented 67.9% of cross-reactive test lines. Cross-reactivity was not associated with detecting antigens, patient categories or disease (sub)groups, except for schistosomiasis (two products with ≥60% cross-reactivity). The high cross-reactivity for malaria, schistosomiasis and—to a lesser extent—dengue calls for risk mitigation when using COVID-19 Ab RDTs in co-endemic regions.

Lack of perception regarding risk of dengue and day-active mosquitoes in Finnish travellers

Background: An increasing number of international travellers are at risk for dengue infection. We analysed the characteristics of Finnish travellers with recently acquired dengue infections.Methods: Notified dengue infections from 2016 to 2019 were obtained from the Finnish National Infectious Disease Register. We developed a questionnaire and invited individuals diagnosed with dengue to provide information on countries and areas of infection, travel characteristics, risk perception and use of protective measures.Results: Almost all infections (94%, 127/135) were acquired in Asian countries, most in Thailand (78/135, 58%). The Maldives had the highest crude risk after adjusting for the number of travellers (55.6/100,000). Most trips were pre-booked holidays (93/111, 84%) and 62% (69/111) had a duration of 14-21 days with time spent mostly on the beach (78/111, 70%). The majority of travellers were not aware of the risk of dengue infection before travelling (67/111, 60%) and had not sought pre-travel advice (72/111, 65%). The majority applied some protective measures (71/111, 64%) but mainly after sunset (64/111, 58%).Conclusions: Most dengue infections in Finnish travellers were acquired at popular destinations in Southeast Asia, especially Thailand. Our study showed that there was low awareness regarding the risk of contracting the infection. In addition, many travellers reported inadequate use of protective measures. This calls for further public health actions, such as raising awareness of day-active mosquitoes, of risk at popular travelling destinations and the correct way of applying anti-vectorial measures.

The surveillance of four mosquito-borne diseases in international travelers arriving at Guangzhou Baiyun International Airport, China, 2016–2017

BACKGROUND

Little comprehensive analysis combining epidemiological and clinical data has been done with mosquito-borne diseases imported into Guangzhou by air travelers.

METHODS

We screened international travelers (body temperature >36.5 °C) arriving at Guangzhou Baiyun International Airport, and recorded their epidemiological and clinical information. Whole-blood samples were collected for laboratory diagnosis of dengue virus (DENV), chikungunya virus (CHIKV), zika virus (ZIKV) infections and malaria.

RESULTS

Between March 1, 2016 and December 31, 2017, 155 (6.6%) cases (100 of DENV, 21 of CHIKV, 1 of ZIKV, 34 of malaria, including one co-infection of DENV and CHIKV) were identified among 2350 febrile travelers. DENV (90.0%) and CHIKV (100.0%) cases mainly came from Southern and Southeast Asia. Malaria cases (91.2%) mainly came from sub-Saharan Africa. Traveling abroad (28/74, 37.8%) and living/working abroad (11/22, 50.0%) were the most common causes of DENV infection and malaria for Chinese, respectively. Cases with these four mosquito-borne diseases were more likely to have nervous, musculoskeletal and skin symptoms and signs than other febrile diseases (P < 0.001).

CONCLUSIONS

It is important to strengthen the surveillance of mosquito-borne diseases among tourists and workers returning from Southeast Asia, Southern Asia and sub-Saharan Africa, especially those with nervous, musculoskeletal and skin symptoms and signs.

Clinical Features and Laboratory Findings of Travelers Returning to South Australia with Dengue Virus Infection

Reported cases of dengue are rising in South Australia (SA) in travellers returning from dengue-endemic regions. We have undertaken a retrospective analysis to identify the clinical and laboratory characteristics of patients returning to SA with suspected dengue virus (DENV) infection. From 488 requests, 49 (10%) were defined by serology as acute dengue, with the majority of patients (75%) testing as non-structural protein 1 (NS1) and/or IgM positive. Dengue was most commonly acquired in Indonesia (42.9%) with clinical features of fever (95%), headache (41%) and myalgia/arthralgia (56%). The presence of rash (36%) and laboratory findings of neutropenia, leukopenia, thrombocytopenia, but not elevated C-reactive protein, were distinct from findings in DENV-seronegative patients. Available dengue seropositive samples were analysed by RT-PCR, with 14/32 (43.8%) positive by a serotype non-specific DENV assay, but 28/32 positive (87.5%) when also assessed by serotype-specific RT-PCR. Serotype analysis revealed the predominance of DENV-1 and DENV-2 and the presence of DENV-3, but not DENV-4 or Zika virus (ZIKV). Thus, dengue in returned travellers in SA presents in a manner consistent with World Health Organization (WHO) definitions, with symptoms, travel history and laboratory results useful in prioritising the likelihood of dengue. This definition will assist the future management in DENV-non-endemic regions, such as SA.

Imported Dengue Infection in a Spanish Hospital with a High Proportion of Travelers from Africa: A 9-Year Retrospective Study

Epidemiological data on dengue in Africa are still scarce. We investigated imported dengue infection among travelers with a high proportion of subjects from Africa over a 9-year period. From January 2005 to December 2013, blood samples from travelers with clinical suspicion of dengue were analyzed. Dengue was diagnosed using serological, antigen detection, and molecular methods. Subjects were classified according to birthplace (Europeans versus non-Europeans) and last country visited. Overall, 10,307 serum samples corresponding to 8,295 patients were studied; 62% were European travelers, most of them from Spain, and 35.9% were non-Europeans, the majority of whom were born in Africa (mainly Equatorial Guinea) and Latin America (mainly Bolivia, Ecuador, and Colombia). A total of 492 cases of dengue were identified, the highest number of cases corresponding to subjects who had traveled from Africa (N = 189), followed by Latin America (N = 174) and Asia (N = 113). The rate of cases for Africa (4.5%) was inferior to Asia (9%) and Latin America (6.1%). Three peaks of dengue were found (2007, 2010, and 2013) which correlated with African cases. A total of 2,157 of past dengue infections were diagnosed. Non-Europeans who had traveled from Africa had the highest rate of past infection (67.8%), compared with non-Europeans traveling from Latin America (38.7%) or Asia (35%). Dengue infection in certain regions of Africa is underreported and the burden of the disease may have a magnitude similar to endemic countries in Latin America. It is necessary to consider dengue in the differential diagnosis of other febrile diseases in Africa.

Neutralizing and enhancing antibody responses to five genotypes of dengue virus type 1 (DENV-1) in DENV-1 patients

Dengue virus (DENV) has four distinct serotypes, DENV-1-4, with four to six genotypes in each serotype. The World Health Organization recommends tetravalent formulations including one genotype of each serotype as safe and effective dengue vaccines. Here, we investigated the impact of genotype on the neutralizing antibody responses to DENV-1 in humans. Convalescent sera collected from patients with primary infection of DENV-1 were examined for neutralizing antibody against single-round infectious particles of the five DENV-1 genotypes (GI-GV). In both GI- and GIV-infected patients, their neutralizing antibody titres against the five genotypes were similar, differing ≤4-fold from the homogenotypic responses. The enhancing activities against the five genotypes were also similar in these sera. Thus, the genotype strains of DENV-1 showed no significant antigenic differences in these patients, suggesting that GI- or GIV-derived vaccine antigens should induce equivalent levels of neutralizing antibodies against all DENV-1 genotypes.

Clinical Utility of the Nonstructural 1 Antigen Rapid Diagnostic Test in the Management of Dengue in Returning Travelers With Fever

Background

Rapid diagnostic test (RDT) detecting the nonstructural 1 (NS1) antigen is increasingly used for dengue diagnosis in endemic and nonendemic settings, but its clinical utility has not been studied in travel clinic practice.

Methods

From August 2012 to July 2016, travelers returning from the tropics with fever were evaluated in the Institute of Tropical Medicine (Antwerp, Belgium) with the routine use of NS1 antigen RDT that provided results within 1 hour. We determined the diagnostic performance, assessed the management of patients with a positive RDT result, and compared it with that of historical cases of dengue diagnosed from 2000 to 2006, when only antibody detection assays were available.

Results

Of 335 travelers evaluated for fever, 54 (16%) were diagnosed with dengue, including 1 severe case. Nonstructural 1 antigen RDT was performed in 308 patients. It was truly positive in 43 of 52 tested dengue cases and falsely positive in only 1 of the 256 nondengue cases; therefore, sensitivity was 82.7% (95% confidence interval [CI], 74.4%–93.0%) and specificity was 99.6% (95% CI, 98.8%–100%). Only 3 (7%) of the 43 febrile travelers “immediately” diagnosed by RDT were admitted, and only 2 (5%) were given empirical antibacterial treatment, without adverse outcome. Admission and antibiotic prescription rates were significantly higher in the historical cases (n = 43) diagnosed by antibody detection (33%, P = .006 and 26%, P = .014, respectively), although the frequency of severe dengue was similar.

Conclusions

In our practice, the diagnostic performance of NS1 antigen RDT substantially contributed in withholding unnecessary hospitalization and antibiotherapy in dengue patients.

Clinical Survey of Dengue Virus Circulation in the Republic of Djibouti between 2011 and 2014 Identifies Serotype 3 Epidemic and Recommends Clinical Diagnosis Guidelines for Resource Limited Settings

Dengue virus is endemic globally, throughout tropical and sub-tropical regions. While the number of epidemics due to the four DENV serotypes is pronounced in East Africa, the total number of cases reported in Africa (16 million infections) remained at low levels compared to Asia (70 million infections). The French Armed forces Health Service provides epidemiological surveillance support in the Republic of Djibouti through the Bouffard Military hospital. Between 2011 and 2014, clinical and biological data of suspected dengue syndromes were collected at the Bouffard Military hospital and analyzed to improve Dengue clinical diagnosis and evaluate its circulation in East Africa. Examining samples from patients that presented one or more Dengue-like symptoms the study evidenced 128 Dengue cases among 354 suspected cases (36.2% of the non-malarial Dengue-like syndromes). It also demonstrated the circulation of serotypes 1 and 2 and reports the first epidemic of serotype 3 infections in Djibouti which was found in all of the hospitalized patients in this study. Based on these results we have determined that screening for Malaria and the presence of the arthralgia, gastro-intestinal symptoms and lymphopenia < 1,000cell/ mm3 allows for negative predictive value and specificity of diagnosis in isolated areas superior to 80% up to day 6. This study also provides evidence for an epidemic of Dengue virus serotype 3 previously not detected in Djibouti.

Dengue virus is emerging worldwide, however, little is known about the burden of Dengue in Africa. Effectively, only sporadic cases and few epidemics have been reported in the last 30 years. This descriptive study reports clinical and biological data of Dengue-suspected cases analyzed in the Bouffard military hospital of Djibouti from 2011–2014. It also confirms the circulation of Dengue virus serotypes 1 and 2 and reports the first epidemic of Dengue virus serotype 3 infections in Djibouti. Directions for diagnosis are offered to practitioners working in resource limited settings and dealing with a Dengue-like syndrome of less than seven days and negative for malaria.