Risk Factors for Bunyavirus-Associated Severe Fever with Thrombocytopenia Syndrome: A Community-Based Case-Control Study

Abstract

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by a novel bunyavirus. Previous studies about risk factors for SFTSV infection have yielded inconsistent results, and behavior factors have not been fully clarified.MethodsA community-based, 1:4 matched case-control study was carried out to investigate the risk factors for SFTS in China. Cases of SFTS were defined as laboratory-confirmed cases that tested positive for real-time PCR (RT-PCR) for severe fever with thrombocytopenia syndrome bunyavirus (SFTSV) or positive for IgM antibodies against SFTSV. Controls of four neighborhood subjects were selected by matching for sex, age, and occupation. Standardized questionnaires were used to collect detailed information about their demographics and risk factors for SFTSV infection.ResultsA total of 334 subjects participated in the study including 69 cases and 265 controls. The median age of the cases was 59.5 years, 55.1% were male, and 87.0% were farmers. No differences in demographics were observed between cases and controls. In the final multivariate analysis, tick bites two weeks prior to disease onset (OR = 8.04, 95%CI 3.34–19.37) and the presence of weeds and shrubs around the house (OR = 3.46, 95%CI 0.96–12.46) were found to be risk factors for SFTSV infection; taking preventative measures during outdoor activities (OR = 0.12, 95%CI 0.01–1.01) provided greater protection from SFTSV infection.ConclusionsOur results further confirm that SFTSV is transmitted by tick bites and prove that preventative measures that reduce exposure to ticks can prevent SFTSV infection. More efforts should be directed toward health education and behavior change for high-risk populations, especially outdoor workers, in SFTS endemic areas.

A Cluster of Bunyavirus-Associated Severe Fever With Thrombocytopenia Syndrome Cases in a Coastal Plain Area in China, 2015: Identification of a Previously Unidentified Endemic Region for Severe Fever With Thrombocytopenia Bunyavirus

“…SFTS has also been reported in South Korea and Japan [6, 7]. There is no licensed vaccine or therapeutic against SFTSV currently, and avoiding tick exposure is an important way to prevent SFTSV infection [8, 9]. The disease was listed as 1 of the 9 infectious diseases on the World Health Organization priority list in 2017 because of a substantial risk to public health [10].…”

“…Exposure to and bites from infected ticks are thought to be the primary transmission route of SFTSV [8, 9], and secondary cases can be caused by human-to-human transmission, probably through inhalation of virus-containing aerosol [19] and direct contact with blood or bloody secretions bearing SFTSV [20, 21]. The natural foci are thus the basis for the survival, sustaining, and transmission of SFTSV, constituting a potential epidemiological danger.…”

Viral hemorrhagic fevers due to endotheliopathy-associated disseminated intravascular microthrombosis and hepatic coagulopathy: pathogenesis based on “two activation theory of the endothelium”

“…Although viral hemorrhagic fevers commonly occur with etiologyundetermined thrombocytopenia in critically ill patients (TCIP) [1][2][3][6][7][8][9], its relationship to bleeding is not clearly determined because thrombocytopenia is typically mild to moderately severe and it alone can't be accountable for the severe hemorrhagic disorder. Thus, thrombocytopenia has not entered as a serious issue in caring of viral hemorrhagic fevers other than platelet transfusion to maintain it at a safe level.…”

Impact of an intervention programme on knowledge, attitudes and practices of population regarding severe fever with thrombocytopenia syndrome in endemic areas of Lu'an, China

“…Previous studies have demonstrated that people who work outdoors and/or live in mountainous or hilly rural areas were considered as a high-risk population and preventative measures that reduce exposure to ticks can prevent SFTSV infection [7–9]. Owing to the unavailability of vaccines against SFTS and the fatal outcomes of the syndrome, considerable attention should be paid to promoting and strengthening health education and behavioral change among high-risk populations, especially for people who work outdoors in the SFTS endemic areas.…”