Influenza and COVID-19 coinfection: Report of six cases and review of the literature

Coronavirus disease 2019 (COVID-19) pandemic caused infection in a season when influenza is still prevalent. Both viruses have similar transmission characteristics and common clinical manifestations. Influenza has been described to cause respiratory infection with some other respiratory pathogens. However, the information of COVID-19 and influenza coinfection is limited. In this study, we reported our coinfected cases and reviewed the literature. We included all COVID-19 diagnosed patients. All patients with a presumed diagnosis of COVID-19 were routinely screened for influenza. Their thorax radiology was reviewed for COVID-19-influenza differentiation. During the study period, 1103 patients have been diagnosed with COVID-19. Among them, six patients (0.54%) were diagnosed coinfected with influenza. There have been 28 more coinfected patients reported. Laboratory-based screening studies reported more patients. Thorax radiology findings were compatible with COVID-19 in five and with influenza in one of our patients. Our cases were mild to moderate in severity. The reported cases in the literature included patients died (n = 2) and those living ventilator dependent or under mechanical ventilation. COVID-19 and influenza coinfection is rare. Screening studies report more cases, suggesting that unless screening patients with COVID-19, the coinfection remains undiagnosed and underestimated. Increasing experience in thoracic radiology may contribute to diagnose the responsible virus(es) from the clinical illness. Influenza vaccine for larger population groups can be recommended to simplify clinicians' work.