Although severe fever with thrombocytopenia syndrome (SFTS) was first reported from Japan in 2013, the precise clinical features and the risk factors for SFTS have not been fully investigated in Japan. Ninety-six cases of severe fever with thrombocytopenia syndrome (SFTS) were notified through the national surveillance system between April 2013 and September 2014 in Japan. All cases were from western Japan, and 82 cases (85%) had an onset between April and August. A retrospective observational study of the notified SFTS cases was conducted to identify the clinical features and laboratory findings during the same period. Of 96 notified cases, 49 (51%) were included in this study. Most case-patients were of advanced age (median age 78 years) and were retired or unemployed, or farmers. These case-patients had a history of outdoor activity within 2 weeks before the onset of illness. The median serum C-reactive protein concentration was slightly elevated at admission. Fungal infections such as invasive aspergilosis were found in 10% of these case-patients. Hemophagocytosis was observed in 15 of the 18 case-patients (83%) whose bone marrow samples were available. Fifteen cases were fatal, giving a case-fatality proportion of 31%. The proportion of neurological abnormalities and serum concentrations of lactate dehydrogenase and aspartate aminotransferase were significantly higher in the fatal cases than in the nonfatal cases during hospitalization. Appearance of neurological abnormality may be useful for predicting the prognosis in SFTS patients.

S evere fever with thrombocytopenia syndrome (SFTS) is an emerging tickborne infectious disease, identified in 2009 in the rural areas of Hubei and Henan provinces in China (1,2); a total of 7,419 cases were reported from 23 provinces during 2010-2016 (3). SFTS is endemic not only to China but also to South Korea and Japan (4,5). Huaiyangshan banyangvirus (formerly SFTS virus [SFTSV]), the causative agent of SFTS, belongs to the genus Banyangvirus in the family Phenuiviridae. Although the name of the virus has recently been changed from SFTSV to Huaiyangshan banyangvirus by the International Committee on Taxonomy of Viruses (6), the term SFTSV is still used. SFTSV is found in tick species such as Haemaphysalis longicornis, Amblyomma testudinarium, and Ixodes nipponesis in China, South Korea, and Japan (7-9). Antibodies to SFTSV were detected in wild and domestic animals, such as goats, deer, cattle, dogs, and cats, in SFTS-endemic areas of these 3 countries (10-15). SFTSV is thought to circulate in an

Between 9 May and 4 June 2009, a total of 401 laboratory-confirmed cases of influenza A(H1N1)v virus were reported in Japan, from 16 of the 47 Japanese prefectures. The two areas most affected were Osaka prefecture and Kobe city where outbreaks in high schools occurred leading to school closures. To date all cases have had symptoms consistent with seasonal influenza and no severe or fatal cases have been reported.

We analyzed national surveillance data on influenza-associated encephalopathy (IAE) cases reported in Japan from 2010 through 2015. We found differences in the clinical features of IAE between adults and children. Fatal outcomes were higher in patients aged ≥40 years.

The resurgence of HAV in 2010 can be attributed to importation of two newly emerged HAV genotypes.