Two confirmed cases of severe fever with thrombocytopenia syndrome with pneumonia: implication for a family cluster in East China

Advancements in the Worldwide Detection of Severe Fever with Thrombocytopenia Syndrome Virus Infection from 2009 to 2023

Severe fever with thrombocytopenia syndrome (SFTS) is a growing concern as an emerging tick-borne infectious disease originating from the SFTS virus (SFTSV), a recent addition to the Phlebovirus genus under the family of bunyaviruses. SFTS is typically identified by symptoms such as fever, thrombocytopenia, leukopenia, and gastrointestinal problems, accompanied by a potentially high case fatality rate. Thus, early and accurate diagnosis is essential for effective treatment and disease management. This review delves into the existing methodologies for SFTS detection, including pathogenic, molecular, and immunological technologies.

Recurrent rhabdomyolysis in a patient with a history of rhabdomyolysis due to severe fever with thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is a hemorrhagic fever syndrome that is endemic to East Asia. Here, we describe a case of rhabdomyolysis, thought to have been caused by pemafibrate (which was prescribed for hyperlipidemia) or bacterial infection, in a patient who had experienced SFTS-induced rhabdomyolysis 4 years ago. This case suggests that SFTS causes muscle degeneration and can lead to recurrent rhabdomyolysis as a long-term complication.

The Seroprevalence of Severe Fever with Thrombocytopenia Syndrome: An Epidemiological Study of Korean Veterinary Hospital Workers

Severe fever with thrombocytopenia syndrome (SFTS) is a zoonotic tick-borne infectious disease caused by the SFTS virus (SFTSV). Few studies have assessed SFTS seroprevalence among veterinary hospital staff and their awareness of SFTS. From January to May 2021, serum samples from 103 veterinary hospital staff were tested for SFTS using an enzyme-linked immunosorbent assay (ELISA), an immunofluorescence assay, and a 50% plaque reduction neutralization antibody test, which yielded positive results in four (3.9%), three (2.9%), and two (1.9%) participants, respectively. A questionnaire was used for an epidemiological investigation. ELISA positivity was higher among those who lacked awareness of possible animal-to-human SFTS transmission (p = 0.029). SFTS awareness was significantly lower among veterinary hospital staff than among the veterinarians (p < 0.001). Providing staff with training concerning standard precautions and the use of appropriate personal protective equipment is important.

High C-reactive protein to lymphocyte ratio predicts mortality outcomes of patients with severe fever with thrombocytopenia syndrome: A multicenter study in China

Severe fever with thrombocytopenia syndrome (SFTS) is a life-threatening infectious disease caused by the SFTS virus (SFTSV). This study aimed to evaluate the predictive power of C-reactive protein to lymphocyte ratio (CLR) and establish an early-warning model for SFTS mortality. We retrospectively analyzed hospitalized SFTS patients in six clinical centers from May 2011 to 2022. The efficacy of CLR prediction was evaluated by the receiver operating characteristic (ROC) analysis. A nomogram was established and validated. Eight hundred and eighty-two SFTS patients (median age 64 years, 48.5% male) were enrolled in this study, with a mortality rate of 17.8%. The area under the ROC curve (AUC) of CLR was 0.878 (95% confidence interval [CI]: 0.850-0.903, p < 0.001), which demonstrates high predictive strength. The least absolute shrinkage and selection operator regression selected seven potential predictors. Multivariate logistic regression analysis determined three independent risk factors, including CLR, to construct the nomogram. The performance of the nomogram displayed excellent discrimination and calibration, with significant net benefits in clinical uses. CLR is a brand-new predictor for SFTS mortality. The nomogram based on CLR can serve as a convenient tool for physicians to identify critical SFTS cases in clinical practice.

Analysis of spatial-temporal distribution characteristics and natural infection status of SFTS cases in Hefei from 2015 to 2021

BACKGROUND

To analyze the prevalence and spatial-temporal characteristics of severe fever with thrombocytopenia syndrome (SFTS), clustering mode of transmission, and the serological dynamic detection results in multiple areas in Hefei from 2015 to 2021, and to provide the basis for SFTS prevention and control.

METHOD

Case data were obtained from the Chinese Disease Control and Prevention Information System. Information on the clustering outbreak was obtained from the outbreak investigation and disposal report. Population latent infection rate information was obtained from field sampling in multiple-incidence counties in 2016 and 2021 by multi-stage random sampling. Epi data3.2 and SPSS 16.0 softwares were used to perform a statistical analysis of the data on SFTS cases, and QGIS 3.26 software was used to draw the incidence map with township (street) as unit.

RESULTS

The an average annual reported incidence rate of SFTS in Hefei from 2015 to 2021 was 0.65/100,000, and the case fatality rate was 9.73%. The overall prevalence of SFTS epidemics in Hefei City showed a fluctuating upward trend from 2015 to 2021 (χ2trends = 103.353, P < 0.001). Chaohu City, Feixi County, Feidong County and Lujiang County ranked the top 4 in the city in terms of average annual incidence rate. The number of epidemic-involved towns (streets) kept increasing ((χ2trend = 47.640, P = 0.000)). Co-exposure to ticks accounted for the majority of clustered outbreaks and also human-to-human outbreaks. Population-based latent infection rate surveys were conducted in four SFTS multi-incidence counties, with 385 people surveyed in 2016 and 403 people surveyed in 2021, increasing the population-based latent infection rate from 6.75% to 10.91%, just as the incidence rate increased.

CONCLUSIONS

The incidence rate of SFTS in Hefei is obviously regional, with an expanding trend in the extent of the epidemic involved. Co-exposure to ticks accounted for the majority of clustered outbreaks and the latent infection rate cannot be ignored.

Transmission and mortality risk assessment of severe fever with thrombocytopenia syndrome in China: results from 11-years' study

Background

The transmission and fatal risk of severe fever with thrombocytopenia syndrome (SFTS), an emerging infectious disease first discovered in China in 2009, still needed further quantification. This research aimed to analyze the SFTS clusters and assess the transmission and mortality risk for SFTS.

Methods

Both epidemiological investigation and case reports regarding SFTS clusters in China during 2011–2021 were obtained from the Public Health Emergency Information Management System of the Chinese Center for Disease Control and Prevention Information System. The transmission risk was evaluated by using the secondary attack rate (SAR) and relative risk (RR). Mortality risk factors were analyzed using a logistic regression model.

Results

There were 35 SFTS clusters during 2011–2021 involving 118 patients with a fatality rate of 22.0%. The number of clusters annually increased seasonally from April to September. The clusters mainly occurred in Anhui (16 clusters) and Shandong provinces (8 clusters). The SAR through contact with blood or bloody fluids was much higher than that through contact with non-bloody fluids (50.6% vs 3.0%; χ² = 210.97, P < 0.05), with an RR of 16.61 [95% confidence interval (CI): 10.23–26.97]. There was a statistically significant difference in the SAR between exposure to the blood of a deceased person during burial preparation and exposure to the living patients’ blood (66.7% vs 34.5%; χ² = 6.40, P < 0.05), with an RR of 1.93 (95% CI: 1.11–3.37). The mortality risk factors were a long interval from onset to diagnosis [odds ratio (OR) = 1.385), 95% CI: 1.083–1.772, P = 0.009) and advanced age (OR: 1.095, 95% CI: 1.031–1.163, P = 0.01).

Conclusions

The SFTS clusters showed a high mortality rate and resulted in a high SAR. Contact with a bleeding corpse was associated with a higher infection risk, compared with contacting the blood from living patients. It is important to promote early detection and appropriate case management of patients with SFTS, as well as improved handling of their corpses, to prevent further transmission and mortality.

Graphical abstract

Overview of the immunological mechanism underlying severe fever with thrombocytopenia syndrome (Review)

Severe fever with thrombocytopenia syndrome (SFTS) has been acknowledged as an emerging infectious disease that is caused by the SFTS virus (SFTSV). The main clinical features of SFTS on presentation include fever, thrombocytopenia, leukocytopenia and gastrointestinal symptoms. The mortality rate is estimated to range between 5-30% in East Asia. However, SFTSV infection is increasing on an annual basis globally and is becoming a public health problem. The transmission cycle of SFTSV remains poorly understood, which is compounded by the pathogenesis of SFTS not being fully elucidated. Since the mechanism underlying the host immune response towards SFTSV is also unclear, there are no effective vaccines or specific therapeutic agents against SFTS, with supportive care being the only realistic option. Therefore, it is now crucial to understand all aspects of the host-virus interaction following SFTSV infection, including the antiviral states and viral evasion mechanisms. In the present review, recent research progress into the possible host immune responses against SFTSV was summarized, which may be useful in designing novel therapeutics against SFTS.

The Frequency and Patterns of Post-COVID-19 Vaccination Syndrome Reveal Initially Mild and Potentially Immunocytopenic Signs in Primarily Young Saudi Women

Vaccination is the most promising approach for ending or containing the SARS-CoV-2 pandemic. However, serious post-COVID-19 vaccine reactions, including immunocytopenia (ITP) syndrome, have been increasingly reported. Several factors cause increased risks including multiple doses, age-dependent heterogeneity in immune-responses, platelet cross-reactions with microbial components, and Long-COVID syndrome. Thus, in the absence of widely available specific therapeutics, vigilance is important while more studies are needed. Using a structured questionnaire sent to different regions in Saudi Arabia, we conducted a comprehensive investigation on the frequency, rates, disease patterns, and patient demographics of post-COVID-19 vaccine side effects on febrile patients after administration three major vaccines. Results indicated that the majority of respondents administered Pfizer BioNtech vaccine (81%, n = 809); followed by AstraZeneca (16%, n = 155); and Moderna (3%, n = 34). Overall 998 participants, 74% (n = 737) showed no serious symptoms; however, 26.2% (n = 261) revealed typical syndromes. In a focused group of 722 participants, the following rates were identified: shortness of breath (20%), bruises or bleeding (18%), inattention (18%), GIT symptoms (17.6%), skin irritation (8.6%), and anosmia and ageusia (8%) were the most prominent among those who showed typical symptoms. The onset time was mostly between 1–3 days in 49% (n = 128), followed by 4–7 days in 21.8% (n = 57), 8–14 days in 16.5% (n = 43), and more than a month in 12.6% (n = 33). The onsets occurred mostly after the first, second, or both doses, 9%, 10%, and 7% of participants, respectively. The frequency of symptoms was significantly higher after Moderna® vaccine (p-value = 0.00006) and it was significantly lower in participants who received Pfizer (p-value = 0.00231). We did not find significant difference in symptoms related to differences in regions. Similarly, the region, age, sex, education, and nationality had no influence on the dose and onset timings. The findings of this study have significant clinical implications in disease management strategies, preventive measures, and vaccine development. Future vertical studies would reveal more insights into the mechanisms of post-COVID-19 vaccine syndrome.

The Endless Wars: Severe Fever With Thrombocytopenia Syndrome Virus, Host Immune and Genetic Factors

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging arboviral infectious disease with a high rate of lethality in susceptible humans and caused by severe fever with thrombocytopenia syndrome bunyavirus (SFTSV). Currently, neither vaccine nor specific antiviral drugs are available. In recent years, given the fact that both the number of SFTS cases and epidemic regions are increasing year by year, SFTS has become a public health problem. SFTSV can be internalized into host cells through the interaction between SFTSV glycoproteins and cell receptors and can activate the host immune system to trigger antiviral immune response. However, SFTSV has evolved multiple strategies to manipulate host factors to create an optimal environment for itself. Not to be discounted, host genetic factors may be operative also in the never-ending winning or losing wars. Therefore, the identifications of SFTSV, host immune and genetic factors, and their interactions are critical for understanding the pathogenic mechanisms of SFTSV infection. This review summarizes the updated pathogenesis of SFTS with regard to virus, host immune response, and host genetic factors to provide some novel perspectives of the prevention, treatment, as well as drug and vaccine developments.

Oral and ocular transmission of severe fever with thrombocytopenia syndrome virus

BACKGROUND

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne bunyavirus that could cause a severe hemorrhagic fever termed SFTS with a high fatality rate of up to 30%. Importantly, SFTSV is frequently transmitted from person-to-person and patients' blood or excreta are considered as the risk factors for transmission of SFTSV. However, the mechanism of person-to-person transmission of SFTSV is still elusive.

METHODS

In this study, wild-type (WT) C57BL/6 J mice and a lethal SFTSV mouse model IFNAR-/- A129 mice were utilized to evaluate whether SFTSV could be transmitted via oral or ocular routes. C57BL/6 J mice were inoculated with cell-cultured SFTSV via oral and ocular inoculation. IFNAR-/- A129 mice were inoculated with cell-cultured SFTSV or SFTSV infected mouse acute sera via oral and ocular inoculation.

RESULTS

We found that SFTSV antibody positive rates in C57BL/6 J mice were 70% (7/10) and 30% (3/10) in the oral inoculation group and ocular inoculation group, respectively on day 21 post SFTSV inoculation. The mortality rates of IFNAR-/- mice with oral and ocular inoculation of cell-cultured SFTSV were 100% and 83.33% (5/6), respectively on day 6 post inoculation. The mortality rates of IFNAR-/- mice with oral and ocular inoculation of SFTSV infected mouse acute serum were 100% and 66.67% (4/6), respectively on day 9 post inoculation.

CONCLUSIONS

Together, our results show that SFTSV can be transmitted effectively through oral and ocular membrane, suggesting exposure to SFTS positive excreta may be a high-risk factor of nosocomial transmission of SFTSV in hospitals and/or families. Family members and healthcare workers should be protected properly during taking care of SFTS patients to prevent SFTSV nosocomial infection.

Epidemiology, clinical characteristics, and treatment of severe fever with thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease caused by a novel phlebovirus (SFTS virus, SFTSV) in the family Phenuiviridae of the order Bunyavirales. The disease causes a wide spectrum of clinical signs and symptoms, ranging from mild febrile disease accompanied by thrombocytopenia and/or leukocytopenia to hemorrhagic fever, encephalitis, multiple organ failure, and death. SFTS was first identified in China and was subsequently reported in South Korea and Japan. The case-fatality rate ranges from 2.7% to 45.7%. Older age has been consistently shown to be the most important predictor of adverse disease outcomes. Older age exacerbates disease mainly through dysregulation of host immune cells and uncontrolled inflammatory responses. Tick-to-human transmission is the primary route of human infection with SFTSV, and Haemaphysalis longicornis is the primary tick vector of SFTSV. Despite its high case-fatality rate, vaccines and antiviral therapies for SFTS are not currently available. The therapeutic efficacies of several antiviral agents against SFTSV are currently being evaluated. Ribavirin was initially identified as a potential antiviral therapy for SFTS but was subsequently found to inefficiently improve disease outcomes, especially among patients with high viral loads. Favipiravir (T705) decreased both time to clinical improvement and mortality when administered early in patients with low viral loads. Anti-inflammatory agents including corticosteroids have been proposed to play therapeutic roles. However, the efficacy of other therapeutic modalities, such as convalescent plasma, is not yet clear.

Associations between Chest CT Abnormalities and Clinical Features in Patients with the Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by the SFTS virus. It involves multiple organ systems, including the lungs. However, the significance of the lung involvement in SFTS remains unclear. In the present study, we aimed to investigate the relationship between the clinical findings and abnormalities noted in the chest computed tomography (CT) of patients with SFTS. The medical records of 22 confirmed SFTS patients hospitalized in five hospitals in Nagasaki, Japan, between April 2013 and September 2019, were reviewed retrospectively. Interstitial septal thickening and ground-glass opacity (GGO) were the most common findings in 15 (68.1%) and 12 (54.5%) patients, respectively, and lung GGOs were associated with fatalities. The SFTS patients with a GGO pattern were elderly, had a disturbance of the conscious and tachycardia, and had higher c-reactive protein levels at admission (p = 0.009, 0.006, 0.002, and 0.038, respectively). These results suggested that the GGO pattern in patients with SFTS displayed disseminated inflammation in multiple organs and that cardiac stress was linked to higher mortality. Chest CT evaluations may be useful for hospitalized patients with SFTS to predict their severity and as early triage for the need of intensive care.

Vectors, Hosts, and the Possible Risk Factors Associated with Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is a disease caused by infection with the SFTS virus (SFTSV). SFTS has become a crucial public health concern because of the heavy burden, lack of vaccines, effective therapies, and high-fatality rate. Evidence suggests that SFTSV circulates between ticks and animals in nature and is transmitted to humans by tick bites. In particular, ticks have been implicated as vectors of SFTSV, where domestic or wild animals may play as the amplifying hosts. Many studies have identified antigens and antibodies against SFTSV in various animals such as sheep, goats, cattle, and rodents. Besides, person-to-person transmission through contact with blood or mucous of an infected person has also been reported. In this study, we reviewed the literature and summarized the vectors and hosts associated with SFTS and the possible risk factors.

Clinical Update of Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an acute febrile illness characterized by fever, leukopenia, thrombocytopenia, and gastrointestinal symptoms such as diarrhea, nausea, and vomiting resulting from infection with the SFTS virus (SFTSV). The SFTSV is transmitted to humans by tick bites, primarily from Haemaphysalis longicornis, Amblyomma testudinarium, Ixodes nipponensis, and Rhipicephalus microplus. Human-to-human transmission has also been reported. Since the first report of an SFTS patient in China, the number of patients has also been increasing. The mortality rate of patients with SFTS remains high because the disease can quickly lead to death through multiple organ failure. In particular, an average fatality rate of approximately 20% has been reported for SFTS patients, and no treatment strategy has been established. Therefore, effective antiviral agents and vaccines are required. Here, we aim to review the epidemiology, clinical manifestations, laboratory diagnosis, and various specific treatments (i.e., antiviral agents, steroids, intravenous immunoglobulin, and plasma exchange) that have been tested to help to cope with the disease.

Development of an RT-LAMP Assay for the Rapid Detection of SFTS Virus

Detection of severe fever with thrombocytopenia syndrome (SFTS) virus (SFTSV) during the early phase of the disease is important for appropriate treatment, infection control, and prevention of further transmission. The reverse transcription loop-mediated isothermal amplification (RT-LAMP) is a nucleic acid amplification method that amplifies the target sequence under isothermal conditions. Here, we developed an RT-LAMP with a novel primer/probe set targeting a conserved region of the SFTSV L segment after extraction of viral RNA (standard RT-LAMP). Both the Chinese and Japanese SFTSV strains, including various genotypes, were detected by the standard RT-LAMP. We also performed RT-LAMP using the same primer/probe set but without the viral RNA extraction step (called simplified RT-LAMP) and evaluated the diagnostic efficacy. The sensitivity and specificity of the simplified RT-LAMP were 84.9% (45/53) and 89.5% (2/19), respectively. The simplified RT-LAMP can detect SFTSV in human sera containing >10^3.5 copies/mL viral RNA. The two RT-LAMP positive but quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) negative samples were positive in the conventional RT-PCR, suggesting that there was no false positive reaction in the RT-LAMP. Both the standard and simplified RT-LAMP are useful for detecting the SFTSV genome in patients during the early phase of the disease.

Epidemiological and clinical characteristics of severe fever with thrombocytopenia syndrome bunyavirus human-to-human transmission

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) was listed as one of the most severe infectious disease by world health organization in 2017. It can mostly be transmitted by tick bite, while human-to-human transmission has occurred on multiple occasions. This study aimed to explore the epidemiological and clinical characteristics and make risk analysis of SFTS human-to-human transmission.

METHODS

Descriptive and spatial methods were employed to illustrate the epidemiological and clinical characteristics of SFTS human-to-human transmission. The risk of SFTS human-to-human transmission was accessed through secondary attack rate (SAR) and basic reproductive number (R0). Logistic regression analysis was used to identify the associated risk factors.

RESULTS

A total of 27 clusters of SFTS human-to-human transmission were reported in China and South Korea during 1996-2019. It mainly occurred among elder people in May, June and October in central and eastern China. The secondary cases developed milder clinical manifestation and better outcome than the index cases. The incubation period was 10.0 days (IQR:8.0-12.0), SAR was 1.72%-55.00%, and the average R0 to be 0.13 (95%CI:0.11-0.16). Being blood relatives of the index case, direct blood/bloody secretion contact and bloody droplet contact had more risk of infection (OR = 6.35(95%CI:3.26-12.37), 38.01 (95%CI,19.73-73.23), 2.27 (95%CI,1.01-5.19)).

CONCLUSIONS

SFTS human-to-human transmission in China and South Korea during 1996-2019 had obvious spatio-temporal distinction. Ongoing assessment of this transmission risk is crucial for public health authorities though it continues to be low now.

Pathological Characteristics of a Patient with Severe Fever with Thrombocytopenia Syndrome (SFTS) Infected with SFTS Virus through a Sick Cat's Bite

A woman in her fifties showed symptoms of fever, loss of appetite, vomiting, and general fatigue 2 days after she was bitten by a sick cat, which had later died, in Yamaguchi prefecture, western Japan, in June 2016. She subsequently died of multiorgan failure, and an autopsy was performed to determine the cause of death. However, the etiological pathogens were not quickly identified. The pathological features of the patient were retrospectively re-examined, and the pathology of the regional lymph node at the site of the cat bite was found to show necrotizing lymphadenitis with hemophagocytosis. The pathological features were noted to be similar to those of patients reported to have severe fever with thrombocytopenia syndrome (SFTS). Therefore, the lymph node section was retrospectively tested immunohistochemically, revealing the presence of the SFTS virus (SFTSV) antigen. The sick cat showed similar symptoms and laboratory findings similar to those shown in human SFTS cases. The patient had no history of tick bites, and did not have skin lesions suggestive of these. She had not undertaken any outdoor activities. It is highly possible that the patient was infected with SFTSV through the sick cat’s bite. If a patient gets sick in an SFTS-endemic region after being bitten by a cat, SFTS should be considered in the differential diagnosis.

Risk factors for person-to-person transmission of severe fever with thrombocytopenia syndrome

OBJECTIVE

To determine the risk factors for person-to-person transmission of severe fever with thrombocytopenia syndrome (SFTS).

DESIGN

Studies reporting the person-to-person transmission or cluster infection of SFTS were identified and included for risk-factor analyses.

METHODS

Risk factors were investigated by analyzing characteristics of index patients who caused cluster infection and correlation between exposure history and secondary infection.

RESULTS

Analyses of 23 clusters of SFTS infections indicated that all index patients died and that they all had a symptom of bleeding 24 hours before death. Of 89 secondary cases, 82% had been exposed to the index patients' blood. The blood-contact-specific secondary attack rate was 62.4% (73 of 117). The risk relative value was 25 (95% CI, 15-42); thus, the probability of a person getting infected was 25 times more likely when they had contacted blood than when they had not.

CONCLUSION

Exposure to blood of SFTS patients is the highest risk factor for person-to-person infection with SFTSV. SFTS patients' families and healthcare workers should be educated to handle SFTS patients properly and safely to prevent the spread of SFTSV.

Detection of viral RNA in diverse body fluids in an SFTS patient with encephalopathy, gastrointestinal bleeding and pneumonia: a case report and literature review

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease that commonly has a lethal course caused by the tick-borne Huaiyangshan banyang virus [former SFTS virus (SFTSV)]. The viral load in various body fluids in SFTS patients and the best infection control measure for SFTS patients have not been fully established.

CASE PRESENTATION

A 79-year-old man was bitten by a tick while working in the bamboo grove in Nagasaki Prefecture in the southwest part of Japan. Due to the occurrence of impaired consciousness, he was referred to Nagasaki University Hospital for treatment. The serum sample tested positive for SFTSV-RNA in the genome amplification assay, and he was diagnosed with SFTS. Furthermore, SFTSV-RNA was detected from the tick that had bitten the patient. He was treated with multimodal therapy, including platelet transfusion, antimicrobials, antifungals, steroids, and continuous hemodiafiltration. His respiration was assisted with mechanical ventilation. On day 5, taking the day on which he was hospitalized as day 0, serum SFTSV-RNA levels reached a peak and then decreased. However, the cerebrospinal fluid collected on day 13 was positive for SFTSV-RNA. In addition, although serum SFTSV-RNA levels decreased below the detectable level on day 16, he was diagnosed with pneumonia with computed tomography. SFTSV-RNA was detected in the bronchoalveolar lavage fluid on day 21. By day 31, he recovered consciousness completely. The pneumonia improved by day 51, but SFTSV-RNA in the sputum remained positive for approximately 4 months after disease onset. Strict countermeasures against droplet/contact infection were continuously conducted.

CONCLUSIONS

Even when SFTSV genome levels become undetectable in the serum of SFTS patients in the convalescent phase, the virus genome remains in body fluids and tissues. It may be possible that body fluids such as respiratory excretions become a source of infection to others; thus, careful infection control management is needed.

Comparison of chest radiographic findings between severe fever with thrombocytopenia syndrome and scrub typhus: Single center observational cross-sectional study in South Korea

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by SFTS virus (SFTSV) which involves multiple organ systems, including lungs. However, there is limited data on lung involvement of SFTS. Therefore, the present study investigated the chest radiographic findings of SFTS, including computed tomography (CT), and compared these with those of scrub typhus, which is the most common tick-borne illness in South Korea and share risk factors and occur in similar settings.Medical records of patients with confirmed SFTS and scrub typhus in a tertiary hospital in Seoul (South Korea), between January 2014 and June 2018, were reviewed. Initial chest radiography and CT were reviewed by 2 experienced radiologists.A total of 39 patients with SFTS and 101 patients with scrub typhus were analyzed. All patients except 3 patients with scrub typhus in both groups received chest radiography. Cardiomegaly (90%) and patchy consolidation with ground glass opacity (GGO) pattern (31%) were more common in SFTS group than scrub typhus group (20%, P < .001 and 2%, P < .001, respectively). About half of each group received chest CT. Consolidation (29%) and pericardial effusion (24%) were more common in SFTS group than scrub typhus group (6%, P = .02 and 4%, P = .008, respectively). Interstitial thickening in chest radiography (58%) and chest CT (65%) was more frequent in scrub typhus group than SFTS group (18%, P < .001 and 19%, P < .001, respectively).Cardiomegaly with/without pericardial effusion and patchy consolidation with GGO pattern were more frequent in SFTS group, whereas interstitial thickening was more frequent in scrub typhus group. These findings will assist the early differentiation of SFTS from scrub typhus.

Immune Modulation and Immune-Mediated Pathogenesis of Emerging Tickborne Banyangviruses

In the last decade, the emergence of several, novel tickborne viruses have caused significant disease in humans. Of interest are the tickborne banyangviruses: Severe fever with thrombocytopenia syndrome virus (SFTSV), Heartland virus (HRTV), and Guertu virus (GTV). SFTSV and HRTV infection in humans cause viral hemorrhagic fever-like disease leading to mortality rates ranging from 6–30% of the cases. The systemic inflammatory response syndrome (SIRS) associated with SFTSV infection is hypothesized to contribute significantly to pathology seen in patients. Despite the severe disease caused by HRTV and SFTSV, there are no approved therapeutics or vaccines. Investigation of the immune response during and following infection is critical to the generation of fully protective vaccines and/or supportive treatments, and overall understanding of viral immune evasion mechanisms may aid in the development of a new class of therapeutics.

Dyspnea and Wheezing as the Earliest Manifestations of Severe Fever with Thrombocytopenia Syndrome: The First Case Report

A 64-year-old Japanese woman developed fatigue, dyspnea, and wheezing in July. Although she had been undergoing treatment for chronic obstructive pulmonary disease for six days, she was transferred to our hospital with delirium and diarrhea. On admission, she had an eschar of 3 mm in diameter on her anterior chest. Polymerase chain reaction of her blood and eschar specimens led to the diagnosis of severe fever with thrombocytopenia syndrome. Chest computed tomography showed ground-glass opacities, suggesting noncardiogenic pulmonary edema or viral pneumonia. This is the first case report of severe fever with thrombocytopenia syndrome beginning with dyspnea and wheezing.

Shedding and Transmission Modes of Severe Fever With Thrombocytopenia Syndrome Phlebovirus in a Ferret Model

BACKGROUND

Although human-to-human transmission of severe fever with thrombocytopenia syndrome phlebovirus (SFTSV) via direct contact with body fluids has been reported, the role of specific body fluids from SFTSV-infected hosts has not been investigated in detail.

METHODS

To demonstrate the virus transmission kinetics in SFTSV-infected hosts, we adapted the ferret infection model and evaluated the virus shedding periods, virus titers, and transmission modes from various specimens of infected ferrets.

RESULTS

Large amounts of infectious SFTSV are shed through nasal discharge, saliva, and urine from SFTSV-infected ferrets. Virus could be detected from 2 dpi and persisted until 12 dpi in these specimens, compared with the relatively short virus-shedding period in sera. Further, transmission studies revealed that SFTSV can be transmitted to close direct and indirect contact naïve animals through various mediums, especially through contact with serum and urine. Further, ferrets contacted with human urine specimens from SFTSV-positive patients were successfully infected with SFTSV, suggesting that urine specimens could be a source of SFTSV infection in humans.

CONCLUSIONS

Our results demonstrate that the SFTSV can be shed in various body fluids for more than 12 days and that these specimens could be a source for direct or indirect transmission through close personal contact.

Severe fever with thrombocytopenia syndrome can masquerade as hemorrhagic fever with renal syndrome

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral hemorrhagic fever with a high fatality rate and high frequency of person-to-person transmission and is caused by SFTSV, a tick-borne Phlebovirus. Because SFTS has similar clinical manifestations and epidemic characters (such as spatial and temporal distributions) with hemorrhagic fever with renal syndrome (HFRS) in China, we reason that SFTS patients might be misdiagnosed as HFRS.

Methodology/principal findings

Acute-phase sera of 128 clinically diagnosed HFRS patients were retrospectively analyzed for Hantavirus IgM antibodies with ELISA. Hantavirus-negative patients’ sera were further analyzed for SFTSV IgM antibodies with ELISA. ELISA showed that 73 of 128 (57.0%) of clinically diagnosed HFRS patients were IgM antibody positive to Hantaviruses. Among the 55 Hantavirus-IgM negative patients, four (7.3%) were IgM antibody positive to SFTSV. The results indicated that the four SFTS patients were misdiagnosed as HFRS. The misdiagnosed SFTS patients had clinical manifestations common to HFRS and were unable to be differentiated from HFRS clinically.

Conclusions

Our study showed that SFTS patients could be clinically misdiagnosed as HFRS. The misdiagnosis of SFTS as HFRS causes particular concern because it may increase the risk of death of SFTS patients and person-to-person transmission of SFTSV without proper care for and isolation of SFTS patients.

SFTS were clinically misdiagnosed as HFRS. It could cause particular concern in China. Physicians could not rely heavily on the exposure history. Both SFTS and HFRS patients are treated based on the clinical diagnosis in China. Laboratory confirmation of both diseases is not performed in clinical hospitals and the patients’ blood was usually submitted to a local or provincial center for disease control and prevention. In most cases the confirmation diagnosis is to provide retrospective information rather than to guide clinical therapy. Therefore, physicians need to carefully differentiate SFTS and HFRS patients because the fatality of SFTS is much higher than HFRS and SFTS is easily spread from person to person by contacting infected blood or even through aerosol.

Fulminant myocarditis associated with severe fever with thrombocytopenia syndrome: a case report

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral infectious disease with high mortality. It causes multiple organ dysfunction; however, myocarditis has never been reported as a complication with SFTS.

Case presentation

A 62-year-old previously healthy woman developed fever, fatigue, diarrhea, and a mild consciousness disorder. She visited a local clinic, and laboratory data showed leukocytopenia, thrombocytopenia, and elevation of the aspartate aminotransferase level. She was transferred to Kagoshima University Hospital and diagnosed as having SFTS by real-time reverse transcription polymerase chain reaction. Subsequently, her blood pressure gradually decreased despite fluid resuscitation and vasopressor administration. Based on elevated toroponin I levels in serum, a transient diffuse left ventricular hypokinesis and wall thickening in echocardiography, diffuse ST elevation in electrocardiography, and exclusion of other heart diseases, she was diagnosed as having fulminant myocarditis. After hemodynamic support with inotropic agents, she recovered near normal cardiac function. She was discharged to home on day 28.

Conclusions

We report the first case of fulminant myocarditis associated with SFTS.