Prolonged coagulation times in severe fever with thrombocytopenia syndrome virus infection, the indicators of heparin-like effect and increased haemorrhagic risk

Prolonged coagulation times, such as activated partial thromboplastin time (APTT) and thrombin time (TT), are common in patients infected with severe fever with thrombocytopenia syndrome virus (SFTSV) and have been confirmed to be related to patient's poor outcome by previous studies. To find out the reason for prolonged coagulation time in patients with SFTSV infection, and whether it predicts haemorrhagic risk or not. Seventy-eight consecutive patients with confirmed SFTSV infection were enrolled in this prospective, single-centre, observational study. Several global and specific coagulation parameters of these patients on admission were detected, and the haemorrhagic events during hospitalization and their outcomes were recorded. Most of the enrolled patients had prolonged APTT (82.1%) and TT (80.8%), normal prothrombin time (83.3%) and intrinsic coagulation factors above haemostatic levels (97.4%). The heparin-like effect was confirmed by a protamine neutralization test and anti-Xa activity detection in most patients. Interestingly, the APTT and TT results were significantly positively correlated with the levels of endothelial markers and viral load, respectively. The APTT was independently associated with the haemorrhage of patients. The prolonged APTT and TT of SFTS patients may mainly be attributed to endogenous heparinoids and are associated with increased haemorrhagic risk.

Effect of fasting plasma glucose level in severe fever and thrombocytopenia syndrome patients without diabetes

Hyperglycemia is correlated with worse in-hospital outcomes in acute infectious diseases such as coronavirus disease 2019 (COVID-19) and severe fever with thrombocytopenia syndrome (SFTS). This study assessed the relationship between fasting plasma glucose (FPG) levels and in-hospital mortality, disease type, and secondary infections among individuals with SFTS without preexisting diabetes. The clinical data and laboratory results upon admission of 560 patients with SFTS without preexisting diabetes meeting the inclusion criteria at Wuhan Union Hospital were collected. FPG levels in surviving patients with SFTS subjects were significantly lower than those in patients with SFTS who had died (P<0.0001). In multivariate Cox regression, high FPG level (≥11.1 mmol/L) was a risk factor independently associated with the in-hospital death of patients with SFTS without preexisting diabetes. Similarly, the FPG levels in general patients with SFTS were significantly lower than those in patients with severe SFTS (P<0.0001). Multivariate logistic regression identified high FPG level (7.0-11.1 mmol/L) as a risk factor independently associated with SFTS severity. While FPG levels were comparable between patients with SFTS with and without secondary infection (P = 0.5521), logistic regression analysis revealed that high FPG levels were not a risk factor for secondary infection in patients with SFTS without preexisting diabetes. High FPG level on admission was an independent predictor of in-hospital death and severe disease in individuals with SFTS without preexisting diabetes. FPG screening upon admission and glycemic control are effective methods for improving the prognosis of patients with SFTS.

Application of a decision tree model in the early identification of severe patients with severe fever with thrombocytopenia syndrome

Background

Severe fever with thrombocytopenia syndrome (SFTS) is a serious infectious disease with a fatality of up to 30%. To identify the severity of SFTS precisely and quickly is important in clinical practice.

Methods

From June to July 2020, 71 patients admitted to the Infectious Department of Joint Logistics Support Force No. 990 Hospital were enrolled in this study. The most frequently observed symptoms and laboratory parameters on admission were collected by investigating patients’ electronic records. Decision trees were built to identify the severity of SFTS. Accuracy and Youden’s index were calculated to evaluate the identification capacity of the models.

Results

Clinical characteristics, including body temperature (p = 0.011), the size of the lymphadenectasis (p = 0.021), and cough (p = 0.017), and neurologic symptoms, including lassitude (p<0.001), limb tremor (p<0.001), hypersomnia (p = 0.009), coma (p = 0.018) and dysphoria (p = 0.008), were significantly different between the mild and severe groups. As for laboratory parameters, PLT (p = 0.006), AST (p<0.001), LDH (p<0.001), and CK (p = 0.003) were significantly different between the mild and severe groups of SFTS patients. A decision tree based on laboratory parameters and one based on demographic and clinical characteristics were built. Comparing with the decision tree based on demographic and clinical characteristics, the decision tree based on laboratory parameters had a stronger prediction capacity because of its higher accuracy and Youden’s index.

Conclusion

Decision trees can be applied to predict the severity of SFTS.

Severe fever with thrombocytopenia syndrome in Hefei: Clinical features, risk factors, and ribavirin therapeutic efficacy

OBJECTIVES

This study described the clinical features, risk factors, factors affecting the outcome of this disease, and ribavirin therapeutic efficacy for severe fever with thrombocytopenia syndrome (SFTS) patients in Hefei.

METHODS

Between April 2020 and July 2020, 62 cases admitted to the First Affiliated Hospital of Anhui Medical University were included in this study. Serum samples were collected from all patients, after which diagnosis was made via reverse transcription-polymerase chain reaction and via the use of a colloidal gold immunochromatography assay approach.

RESULTS

In multivariate analysis, the following factors were determined as risk factors for SFTS: Being a farmer (odds ratio [OR], 3.033), working in areas with weeds and shrubs (OR, 2.807), and being bitten by a tick (OR, 6.64). The rates of confusion, neck stiffness, viral encephalopathy, and the presence of liver damage were higher in the patients who died than that in the surviving ones. Additionally, the median of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, creatine phosphokinase, activated partial thromboplastin time, D-dimer, fibrinogen degradation products, creatinine, and urea was also higher in the patients who died. One of the 15 patients treated with ribavirin in the early stage could not survive (6.7%), whereas 11 of the 35 patients treated with ribavirin in the late stage could not survive (31.4%); this difference was statistically significant. However, there was no significant difference in mortality between the untreated group and the other two groups (i.e., patients who started antiviral treatment <5 days from the onset and those who started antiviral treatment ≥5 days from the onset). Moreover, there was no positive effect determined on clinical or laboratory parameters in SFTS patients treated with ribavirin. Also, it was observed that leukocyte levels and platelet levels took longer to return to normal.

CONCLUSIONS

In Hefei, clinical features, prognostic factors, and risk factors associated with SFTS are similar to those in other areas. Patients who were given ribavirin did not have better survival rates than patients who were not given ribavirin.

Clinical effect and antiviral mechanism of T-705 in treating severe fever with thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS) virus (SFTSV) is an emerging tick-borne virus with high fatality and an expanding endemic. Currently, effective anti-SFTSV intervention remains unavailable. Favipiravir (T-705) was recently reported to show in vitro and in animal model antiviral efficacy against SFTSV. Here, we conducted a single-blind, randomized controlled trial to assess the efficacy and safety of T-705 in treating SFTS (Chinese Clinical Trial Registry website, number ChiCTR1900023350). From May to August 2018, laboratory-confirmed SFTS patients were recruited from a designated hospital and randomly assigned to receive oral T-705 in combination with supportive care or supportive care only. Fatal outcome occurred in 9.5% (7/74) of T-705 treated patients and 18.3% (13/71) of controls (odds ratio, 0.466, 95% CI, 0.174-1.247). Cox regression showed a significant reduction in case fatality rate (CFR) with an adjusted hazard ratio of 0.366 (95% CI, 0.142-0.944). Among the low-viral load subgroup (RT-PCR cycle threshold ≥26), T-705 treatment significantly reduced CFR from 11.5 to 1.6% (P = 0.029), while no between-arm difference was observed in the high-viral load subgroup (RT-PCR cycle threshold <26). The T-705-treated group showed shorter viral clearance, lower incidence of hemorrhagic signs, and faster recovery of laboratory abnormities compared with the controls. The in vitro and animal experiments demonstrated that the antiviral efficacies of T-705 were proportionally induced by SFTSV mutation rates, particularly from two transition mutation types. The mutation analyses on T-705-treated serum samples disclosed a partially consistent mutagenesis pattern as those of the in vitro or animal experiments in reducing the SFTSV viral loads, further supporting the anti-SFTSV effect of T-705, especially for the low-viral loads.

Seroprevalence of Severe Fever with Thrombocytopenia Syndrome Virus in Small-Animal Veterinarians and Nurses in the Japanese Prefecture with the Highest Case Load

Severe fever with thrombocytopenia syndrome virus (SFTSV) is the causative agent of SFTS, an emerging tick-borne disease in East Asia, and is maintained in enzootic cycles involving ticks and a range of wild animal hosts. Direct transmission of SFTSV from cats and dogs to humans has been identified in Japan, suggesting that veterinarians and veterinary nurses involved in small-animal practice are at occupational risk of SFTSV infection. To characterize this risk, we performed a sero-epidemiological survey in small-animal-practice workers and healthy blood donors in Miyazaki prefecture, which is the prefecture with the highest per capita number of recorded cases of SFTS in Japan. Three small-animal-practice workers were identified as seropositive by ELISA, but one had a negative neutralization-test result and so was finally determined to be seronegative, giving a seropositive rate of 2.2% (2 of 90), which was significantly higher than that in healthy blood donors (0%, 0 of 1000; p < 0.05). The seroprevalence identified here in small-animal-practice workers was slightly higher than that previously reported in other high-risk workers engaged in agriculture and forestry in Japan. Thus, enhancement of small-animal-practice workers’ awareness of biosafety at animal hospitals is necessary for control of SFTSV.

Kinetics of Serological Response in Patients with Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is caused by SFTS virus (SFTSV). We investigated the detailed kinetics of serologic response in patients with SFTS. Twenty-eight patients aged ≥18 years were enrolled between July 2015 and October 2018. SFTS was confirmed by detecting SFTSV RNA in their plasma using reverse transcription polymerase chain reaction. SFTSV-specific IgG and IgM were measured using immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA). We found that SFTSV-specific IgG was detected at days 5–9 after symptom onset, and its titer was rising during the course of disease. SFTSV-specific IgM titer peaked at around week 2–3 from symptom onset. The SFTSV-specific seropositive rates for days 5–9, 10–14, 15–19, and 20–24 from symptom onset using IFA and ELISA were 63%, 76%, 90%, and 100%, and 58%, 86%, 100%, and 100%, respectively, for IgG, whereas they were 32%, 62%, 80%, and 100%, and 53%, 62%, 70%, and 100%, respectively, for IgM. The delayed IgM response could be attributed to the low sensitivity of SFTSV-specific IgM IFA or ELISA and/or impaired immune responses. The IgM test using IFA or ELISA that we used in this study is, therefore, insufficient for the early diagnosis of SFTS.

Correlation between thrombocytopenia and host response in severe fever with thrombocytopenia syndrome

Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging infectious disease caused by a novel bunyavirus, SFTS virus (SFTSV), with fatal outcome developed in approximately 17% of the cases. Thrombocytopenia is a hallmark feature of SFTS, and associated with a higher risk of fatal outcome, however, the pathophysiological involvement of platelet in the clinical outcome of SFTS remained under-investigated. In the current study, by retrospectively analyzing 1538 confirmed SFTS patients, we observed that thrombocytopenia was associated with enhanced activation of the cytokine network and the vascular endothelium, also with a disturbed coagulation response. The platelet phenotypes were also extensively altered in the process of thrombocytopenia development of SFTS patients. More importantly, all these disturbed host responses were related to the severity of thrombocytopenia, thus were considered to play in a synergistic way to influence the disease outcome. Moreover, the clinical effect of platelet transfusion was assessed by comparing two groups of patients with or without receiving this therapy. As a result, we observed no therapy effect in altering frequencies of fatal outcome, clinical bleeding development, or dynamic change of platelet count during the hospitalization. It’s suggested that platelet supplementation alone acted a minor role in improving disease outcome, therefore new therapeutic intervention to regulate host response should be proposed. The current results revealed some evidence of interrelationship between platelet count and clinical outcome of SFTS disease from the perspective of activation of the cytokine network, the vascular endothelium, and the coagulation/fibrinolysis system. These evaluations might help to attain a better understanding of the pathogenesis and therapy choice in SFTS.

Thrombocytopenia in SFTSV is a multifactor-process involving a combination of platelet size or morphology alterations, fibrinolysis activation and coagulation abnormalities, increased inflammatory response and endothelial injury. Platelet supplementation alone shows minor role in improving disease, therefore new therapeutic intervention to regulate host response should be proposed.