Influenza 2018/19 season, Japan
Based on the reported sentinel surveillance data, the estimated number of influenza patients who visited medical facilities between week 36 of 2018 and week 17 of 2019 was approximately 12,000,000. From the 2018/19 season, the method of estimation has been improved and is expected to be approximately 0.66-times the previous estimate. According to hospitalized influenza patient surveillance (data from approximately 500 designated sentinel hospitals with ≥300 beds), the number of hospitalized influenza patients (between week 36 of 2018 and week 17 of 2019) was 20,389. Among patients diagnosed as “acute encephalitis (including encephalopathy)” (a category V notifiable infectious disease), the causative pathogen was reported to be influenza virus in 223 (between week 36 of 2018 and week 17 of 2019). Approximately 3,400 excess deaths were observed nationwide in the 2018/19 season, which was estimated to be similar to the average year.