Epidemiological and etiological characteristics of fever, thrombocytopenia and leukopenia syndrome in Henan Province, China, 2011-2012

Evaluation of a community intervention program on knowledge, attitudes, and practices regarding severe fever with thrombocytopenia syndrome in Anhui Province, China

Background

Severe fever with thrombocytopenia syndrome (SFTS) is a novel infectious disease with no specific therapeutics and vaccines. We hypothesize that health education in vulnerable people would ameliorate their knowledge, attitudes and practices (KAP) regarding SFTS and reduce its prevalence.

Methods

A four-stage cluster cross-section study in sixteen community units was performed. Sixteen groups were allocated to the intervention or control groups. A 6 months education program was administrated. The primary outcome was KAP scores 6 months after intervention. Predictors of KAP score changes were also analyzed.

Results

Eight hundred and fifteen valid questionnaires pre-intervention and 767 ones post-intervention were retreated. No significant differences were found in demographic characteristics and KAP scores before intervention. A significant improvement in KAP score (16.8 ± 4.7 vs. 22.0 ± 4.2, p < 0.001) in the intervention group was observed compare with the controls. Educational level and intervention program were the common predictors of KAP score changes.

Conclusions

Education improved KAP scores in SFTS vulnerable people which may contribute to the control of the disease.

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.

Changes in peripheral blood cytokines in patients with severe fever with thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is recognized as an emerging infectious disease. This study aimed to investigate the pathogenic mechanism of SFTS. A total of 100 subjects were randomly included in the study. Cytokine levels were detected by enzyme‐linked immunosorbent assay and the viral load was detected by micro drop digital PCR. The results showed that levels of interleukin‐6 (IL‐6), IL‐8, IL‐10, IFN‐inducible protein‐10 (IP‐10), monocyte chemoattractant protein‐1 (MCP‐1), macrophage inflammatory protein‐1α (MIP‐1α), transforming growth factor‐β1 (TGF‐β1), and regulated upon activation normal T cell expressed and secreted factor (RANTES) differed significantly among the SFTS patient group, healthy people group, and asymptomatic infection group (p < .05). Compared to the healthy people group, the patient group had increased cytokine levels (IL‐6, IL‐10, IP‐10, MCP‐1, and IFN‐γ) but reduced levels of IL‐8, TGF‐β1, and RANTES (p < .0167). IL‐6, IL‐8, IL‐10, IP‐10, MCP‐1, MIP‐1α, TGF‐β1, and the RANTES levels had different trends after the onset of the disease. IL‐6, IL‐10, IP‐10, and MCP‐1 levels in severe patients were higher than those in mild patients (p < .05). There was a positive correlation between viral load and IL‐6 and IP‐10 but a negative correlation between viral load and RANTES. SFTSV could cause a cytokine change: the cytokine levels of patients had different degrees of fluctuation after the onset of the disease. The levels of IL‐6 and IL‐8 in the asymptomatic infection group were found between the SFTS patients group and the healthy people group. The levels of IL‐6, IL‐10, IP‐10, and MCP‐1 in the serum could reflect the severity of the disease, and the levels of IL‐6, IP‐10, and RANTES were correlated with the viral load.

Seroprevalance of antibodies specific for severe fever with thrombocytopenia syndrome virus and the discovery of asymptomatic infections in Henan Province, China

Background

Severe fever with thrombocytopenia syndrome (SFTS) is a severe emerging disease caused by SFTS virus (SFTSV), and the geographical distribution of SFTS has been increasing throughout China in recent years. To assess SFTSV-specific antibody seroprevalence, a cross-sectional study was conducted for healthy people in high SFTS endemic areas of Henan province in 2016.

Methods

This study used a stratified random sampling method to select 14 natural villages as the investigation sites. From April to May 2016, participants completed a questionnaire survey and serum samples were collected. All serum samples were subjected to ELISA to detect SFTSV-specific IgM and IgG. All IgM-positive samples were further tested by real-time RT-PCR, and isolation of virus from serum was attempted. Any participant who was IgM-positive was followed up with a month later to confirm health status.

Results

In total, 1463 healthy people participated in this study. The average seropositive rates for SFTSV-specific IgG and IgM were 10.46% (153/1463) and 0.82% (12/1463), respectively. IgM was detected in 12 individuals, and SFTSV RNA was detected in six of them. Virus was isolated from five of the six SFTSV RNA-positive individuals, and phylogenetic analyses revealed that all five isolates belonged to SFTSV group A. No IgM-positive participants exhibited any symptoms or other signs of illness at the one-month follow up.

Conclusions

This study identified a relatively high incidence of SFTSV-specific antibody seropositivity in healthy people in Xinyang city. Moreover, our data provide the first evidence for asymptomatic SFTSV infections, which may have significant implications for SFTS outbreak control.

Severe fever with thrombocytopenia syndrome (SFTS) is a severe emerging infectious disease caused by SFTS virus (SFTSV) that was first discovered in rural areas of China. Henan province has had the largest number of SFTS cases in China every year since the disease was discovered, however, seropositivity for SFTSV-specific antibodies in healthy people in this region is still not clear. To address this issue, a cross-sectional survey was performed in high endemic areas from April to May 2016. The results showed that SFTSV seroprevalence was relatively high and possibly increasing. Notably, SFTSV RNA, as well as virus itself, was isolated from specimens obtained from healthy people. This study confirmed there are asymptomatic SFTSV infections in humans, and it is the first to report SFTSV isolation from healthy people.

Prevalence of severe fever with thrombocytopenia syndrome virus in animals in Henan Province, China

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by severe fever with thrombocytopenia syndrome virus (SFTSV). SFTSV has been found in humans, ticks and animals, and SFTS has high mortality and increasing prevalence in East Asia. In the study, the samples (heart, liver, lung, kidney, spleen, brain tissue and serum) were collected from 374 domestic animals and 241 wild animals in Pingqiao District and Xinxian County of Xinyang in Henan Province, China. 275 (44.72%, 275/615) animals were positive for anti-SFTSV antibodies, the anti-SFTSV antibodies positive ratios of domestic and wild animals were 43.58% (163/374) and 46.47% (112/241), respectively. There was no significant difference in domestic and wild animals, but significant differences were detected among different species of animals (χ² = 112.59, P < 0.0001). Among 615 animals, 105 (17.07%, 105/615) animals were positive for SFTSV RNA, and only one SFTSV strain was isolated from heart tissue of a yellow weasel. The phylogenetic analysis shows that the sequence from animals belonged to the same group with viral sequences obtained from humans. The animals maybe play a reservoir host in maintaining the life cycle of SFTSV in nature.

Genomes and seroprevalence of severe fever with thrombocytopenia syndrome virus and Nairobi sheep disease virus in Haemaphysalis longicornis ticks and goats in Hubei, China

Ticks are medically-important arthropods that maintain and transmit numerous emerging viruses. China suffers severely from tick-borne viral diseases such as tick-borne encephalitis and severe fever with thrombocytopenia syndrome (SFTS), but the background of tick-borne viruses is very limited. Here we report the virome profiling of ticks and goat sera from SFTS-epidemic areas, and serological investigation of SFTS virus (SFTSV) and Nairobi sheep disease virus (NSDV). Results revealed divergent viruses in ticks and goat sera, including SFTSV and NSDV. Sequence and phylogenetic analyses showed that the SFTSV identified here was most closely related to human SFTSV in sampling and surrounding areas, and the NSDV to the previously identified NSDV from northeast China. Serological investigation of SFTSV infection in goats revealed intensive activity in those areas. Surprisingly, two different methods of NSDV serological investigation showed no sera positive for this virus.

Epidemiological Characteristics and Environmental Risk Factors of Severe Fever with Thrombocytopenia Syndrome in Hubei Province, China, from 2011 to 2016

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne viral disease affecting hundreds of people in China each year. To better understand the epidemiological characteristics and environmental risk factors associated with the incidence of SFTS in Hubei Province, China, we conducted a retrospective epidemiological study and risk assessment of SFTS from 2011 to 2016. Although, the incidence and epidemic areas of SFTS are increasing, the fatality rate has decreased. Elderly farmers are the population most commonly infected with SFTS virus between May and July in the northeast Hubei Province, which seems to be consistent with local agricultural activities and the seasonal abundance of ticks. Spatial scanning showed that regions bordering with Xinyang City, Henan Province accounted for most of the SFTS cases in Hubei Province, and there was a significant association of SFTS incidence with temporal changes in the climate within these clusters. Multivariate modeling analysis identified density of cattle, rain-fed cropland, built-up land, temperature, and relative humidity as independent risk factors for the distribution of SFTS. Future epidemiological and serological studies are warranted to elucidate the dynamics and immunity patterns of local SFTS disease and to optimize interventions.

Score risk model for predicting severe fever with thrombocytopenia syndrome mortality

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging epidemic infectious disease with high mortality in East Aisa, especially in China. To predict the prognosis of SFTS precisely is important in clinical practice.

Methods

From May 2013 to November 2015, 233 suspected SFTS patients were tested for SFTS virus using RT-PCR. Cox regression model was utilized to comfirm independent risk factors for mortality. A risk score model for mortality was constructed based on regression coefficient of risk factors. Log-rank test was used to evaluate the significance of this model.

Results

One hundred seventy-four patients were confirmed with SFTS, of which 40 patients died (23%). Baseline age, serum aspartate aminotransferase (AST) and serum creatinine (sCr) level were independent risk factors of mortality. The area under ROC curve (AUCs) of these parameters for predicting death were 0.771, 0.797 and 0.764, respectively. And hazard ratio (HR) were 1.128, 1.002 and 1.013, respectively. The cutoff value of the risk model was 10. AUC of the model for predicting mortality was 0.892, with sensitivity and specificity of 82.5 and 86.6%, respectively. Log-rank test indicated strong statistical significance (ײ = 88.35, p < 0.001).

Conclusions

This risk score model may be helpful to predicting the prognosis of SFTS patients.

Novel sub-lineages, recombinants and reassortants of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) has been continuously circulating in Eastern Asia in recent years, without the availability of effective vaccines or antiviral drugs, posing a serious threat to public health, particularly in the central-eastern provinces of China. In this study, we isolated and sequenced four new SFTSV strains from Shandong Province identified in 2015. Phylogenetic analysis, with all publicly available L, M and S gene segments, revealed that the four newly described SFTSV strains belonged to genotype C3. In addition, our phylogenetic analyses also identified two potentially novel sub-lineages of SFTSV, tentatively named C6 and J4. Our comprehensive analysis revealed twenty recombination events in fourteen SFTSV genomes and recombination events were found in the S gene segment for the first time. A total of twenty-six strains were probable SFTSV reassortants, including sixteen which were previously unidentified. We further characterised the genetic constellation of these putative reassortants and classified them into twelve different reassortment forms. Our study revealed multiple evolutionary forces acting on SFTSV, responsible for the increasing genetic diversity of this agent, which could potentially alter the antigenicity and pathogenicity of the virus. This calls for an urgent need for intensified surveillance and the development of vaccines and antiviral drugs against this high-consequence pathogen.

A national assessment of the epidemiology of severe fever with thrombocytopenia syndrome, China

First discovered in rural areas of middle-eastern China in 2009, severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne zoonosis affecting hundreds of cases reported in China each year. Using the national surveillance data from 2010 to 2013, we conducted this retrospective epidemiological study and risk assessment of SFTS in China. We found that the incidence of SFTS and its epidemic areas are continuing to grow, but the case fatality rate (CFR) has steadily decreased. SFTS most commonly affected elderly farmers who acquired infection between May and July in middle-eastern China. However, other epidemiological characteristics such as incidence, sex ratio, CFR, and seasonality differ substantially across the affected provinces, which seem to be consistent with local agricultural activities and the seasonal abundance of ticks. Spatial scan statistics detected three hot spots of SFTS that accounted for 69.1% of SFTS cases in China. There was a strong association of SFTS incidence with temporal changes in the climate within the clusters. Multivariate modeling identified climate conditions, elevation, forest coverage, cattle density, and the presence of Haemaphysalis longicornis ticks as independent risk factors in the distribution of SFTS, based on which a predicted risk map of the disease was derived.

The severe fever with thrombocytopenia syndrome bunyavirus (SFTSV) antibody in a highly endemic region from 2011 to 2013: a comparative serological study

A seropositive rate of 6.59% was determined in the highly endemic region for severe fever with thrombocytopenia syndrome. A significant correlation was observed between case incidence and seroprevalence on temporal and geographic levels. Seroprevalence was comparable in the last 3 years, indicating a stable and ongoing circulation of the infection.

Discrimination of novel bunyavirus infection using routine laboratory test

The wide epidemic and high case fatality rate have made severe fever with thrombocytopenia syndrome (SFTS) a significant public health problem. The diagnosis and discrimination of SFTS virus (SFTSV) infection at an early stage of the disease is important for treatment choice. A prospective study was performed in an SFTS reference hospital during 2011-2013. Suspected SFTS patients were recruited and prospectively observed. Comparison between SFTSV-positive and -negative patients was made to identify the parameters that were related to positive detection by discriminant and classification tree analysis. A total of 538 SFTSV-positive and 396 negative patients were recruited and observed. Multiple logistic regression models demonstrated the significant parameters associated with positive detection, including decreased platelet counts and elevated aspartate aminotransferase (AST) level during the first stage (1∼4 days), decreased white blood cell and platelet counts, elevated creatine kinase (CK) and AST levels during the second stage (5∼7 days), and older age, decreased consciousness and elevated CK and AST during the third stage (8-11 days). The classification trees disclosed that the significant predictors for positive SFTSV detection were AST >50.6 U/L and AST/alanine transaminase (ALT) >1.3 at the first stage, CK >257 U/L or 57.7 U/L < CK ≤98.5 U/L with AST/ALT >1.6 at the second stage, as well as CK >630.7 U/L or 114.3 U/L < CK ≤630.7 U/L with decreased consciousness at the third stage. In making the clinically probable diagnosis of SFTS, the supplementation of AST and CK evaluations might remarkably improve the diagnostic capacity of routine laboratory tests, while the leukopenia is of limited use.