Number of Patients with Influenza and COVID-19 Coinfection in a Single Japanese Hospital during the First Wave.

An individual may contract coronavirus disease 2019 (COVID-19) and influenza simultaneously; hence, adequate measures must be undertaken for the next winter in Japan. In preparation for the future, this study aimed to clarify the incidence of influenza coinfection in patients with COVID-19 during the previous winter. We conducted a retrospective study of the medical records of 193 patients diagnosed with COVID-19 between January 31, 2020, and April 23, 2020, in a single hospital. We evaluated the incidence of COVID-19 and influenza coinfection. Using rapid diagnostic testing, we found that no patient with COVID-19 was coinfected with influenza. Coinfection with influenza and COVID-19 was rare during the past winter in Japan.