Tomoki Yoshikawa1, Masayuki Shimojima1, Shuetsu Fukushi1, Hideki Tani1, Aiko Fukuma1, Satoshi Taniguchi1, Harpal Singh1, Yuto Suda1, Komei Shirabe2, Shoichi Toda2, Yukie Shimazu3, Taro Nomachi4, Mutsuyo Gokuden5, Toshiharu Morimitsu6, Katsuyuki Ando7, Akira Yoshikawa8, Miki Kan9, Marina Uramoto10, Hideo Osako11, Kouji Kida12, Hirokazu Takimoto13, Hiroaki Kitamoto14, Fumio Terasoma15, Akiko Honda16, Ken Maeda17, Toru Takahashi18, Takuya Yamagishi19, Kazunori Oishi19, Shigeru Morikawa20, Masayuki Saijo1. 1. Special Pathogens Laboratory, Department of Virology I, National Institute of Infectious Diseases. 2. Yamaguchi Prefectural Institute of Public Health and Environment. 3. Hiroshima Prefectural Technology Research Institute, Public Health and Environment Center. 4. Miyazaki Prefectural Institute for Public Health and Environment. 5. Kagoshima Prefectural Institute for Environmental Research and Public Health. 6. The Public Institute of Kochi Prefecture. 7. Saga Prefectural Institute of Public Health and Pharmaceutical Research. 8. Nagasaki Prefectural Institute for Environmental Research and Public Health, Omura-shi. 9. Ehime Prefectural Institute of Public Health and Environmental Science, Matsuyama-shi. 10. Tokushima Prefectural Public Health, Pharmaceutical and Environmental Sciences Centre. 11. Kumamoto Prefectural Institute of Public Health and Environmental Science, Uto-shi. 12. Okayama Prefectural Institute for Public Health and Environmental Science. 13. Shimane Prefectural Institute of Public Health and Environmental Science, Matsue-shi. 14. Public Health Science Research Center, Hyogo Prefectural Institute of Public Health and Consumer Sciences, Hyogo-ku Kobe-shi. 15. Wakayama Prefectural Research Center of Environment and Public Health. 16. Oita Prefectural Institute of Health and Environment. 17. Laboratory of Veterinary Microbiology, Joint Faculty of Veterinary Medicine, Yamaguchi University. 18. Department of Hematology, Yamaguchi Grand Medical Center, Hofu-shi. 19. Infectious Disease Surveillance Center, National Institute of Infectious Diseases. 20. Department of Veterinary Science, National Institute of Infectious Diseases, Tokyo, Japan.
Abstract
BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne acute infectious disease caused by the SFTS virus (SFTSV). SFTS has been reported in China, South Korea, and Japan as a novel Bunyavirus. Although several molecular epidemiology and phylogenetic studies have been performed, the information obtained was limited, because the analyses included no or only a small number of SFTSV strains from Japan. METHODS: The nucleotide sequences of 75 SFTSV samples in Japan were newly determined directly from the patients' serum samples. In addition, the sequences of 7 strains isolated in vitro were determined and compared with those in the patients' serum samples. More than 90 strains that were identified in China, 1 strain in South Korea, and 50 strains in Japan were phylogenetically analyzed. RESULTS: The viruses were clustered into 2 clades, which were consistent with the geographic distribution. Three strains identified in Japan were clustered in the Chinese clade, and 4 strains identified in China and 26 in South Korea were clustered in the Japanese clade. CONCLUSIONS: Two clades of SFTSV may have evolved separately over time. On rare occasions, the viruses were transmitted overseas to the region in which viruses of the other clade were prevalent.
BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne acute infectious disease caused by the SFTS virus (SFTSV). SFTS has been reported in China, South Korea, and Japan as a novel Bunyavirus. Although several molecular epidemiology and phylogenetic studies have been performed, the information obtained was limited, because the analyses included no or only a small number of SFTSV strains from Japan. METHODS: The nucleotide sequences of 75 SFTSV samples in Japan were newly determined directly from the patients' serum samples. In addition, the sequences of 7 strains isolated in vitro were determined and compared with those in the patients' serum samples. More than 90 strains that were identified in China, 1 strain in South Korea, and 50 strains in Japan were phylogenetically analyzed. RESULTS: The viruses were clustered into 2 clades, which were consistent with the geographic distribution. Three strains identified in Japan were clustered in the Chinese clade, and 4 strains identified in China and 26 in South Korea were clustered in the Japanese clade. CONCLUSIONS: Two clades of SFTSV may have evolved separately over time. On rare occasions, the viruses were transmitted overseas to the region in which viruses of the other clade were prevalent.