How many coinfected patients with influenza and COVID-19 are there in a single Japanese hospital during the first wave?

Kawai, Shoko; Fukushima, Kazuaki; Yomota, Makiko; Fukuda, Akito; Fujiwara, Sho; Tanaka, Masaru; Kobayashi, Taiichiro; Yajima, Keishiro; Hosomi, Yukio; Imamura, Akifumi

Coronavirus disease 2019 (COVID-19) and influenza may infect a person simultaneously; hence, adequate measures must be prepared for the next winter in Japan. In preparation for the future, this study aimed to clarify the rate of influenza coinfection in patients with COVID-19 in previous winter. We conducted a retrospective study of the medical records of 193 patients diagnosed as having COVID-19 between January 31, 2020, and April 23, 2020, in a single hospital. We measured the rate of coinfection with COVID-19 and influenza. We found no patient was coinfected with influenza using rapid diagnostic testing. The occurrence of coinfection with influenza and COVID-19 seems to be rare in the past winter in Japan.