Influenza 2016/17 season, Japan

Based on the reported sentinel surveillance data, the estimated number of influenza patients who attended medical facilities from week 36 of 2016 to week 20 of 2017 (from September 5, 2016 to May 21, 2017) was 16,960,000. According to hospitalized influenza patient surveillance (data from approximately 500 designated sentinel hospitals with ≥300 beds), the number of hospitalized influenza patients during the same period was 15,405, which was 1.25-fold greater than that in the 2015/16 season (12,275 patients). Among patients diagnosed as “acute encephalitis” (a category V notifiable infectious disease), 117 were reported as cases whose causative pathogen was influenza virus (as of May 15, 2017), which was about half of that reported in the previous season (224 in the 2015/16 season).