[Severe fever with thrombocytopenia syndrome: epidemiology, pathophysiology, and development of specific treatment and prevention measures].

Severe fever with thrombocytopenia syndrome (SFTS) was first reported in 2011 as an emerging virus infection caused by a novel Phlebovirus in the Bunyaviridae family [SFTS virus (SFTSV)]. In addition, it was reported to be endemic to Hubei, Henan, Shandong, and Heilongjiang provinces in China. The primary symptoms of SFTS are gastrointestinal symptoms such as fever, general fatigue, nausea, vomiting, and diarrhea. The total blood cell counts in patients with SFTS reveal thrombocytopenia and leukopenia. A woman in her 50s died due to multiorgan failure, intestinal hemorrhage, and hemophagocytosis in the autumn of 2012. She was retrospectively diagnosed with SFTS, suggesting that SFTS was endemic not only to China but also to Japan. Subsequently, SFTS was reported to be endemic to South Korea as well. Approximately 5 years have passed since the discovery of SFTS endemicity in Japan. To date, 40-100 patients with SFTS from the western part of Japan have been reported annually to the National Institute of Infectious Diseases. The case-fatality rate of SFTS is approximately 20%. This high case-fatality rate could be attributed to multiorgan failure, coagulopathy, and hemophagocytosis, which are induced in most patients with SFTS. Reportedly, an antiviral drug, favipiravir, was effective in treating SFTSV infection in an animal infection model. SFTSV has been found to circulate between wild animals and several species of ticks in nature, suggesting that we cannot escape the risk of infection with SFTSV and that SFTS will continue to occur in endemic areas. Hence, the development of specific treatment and preventive measures with SFTS vaccines is imperative.