Co-infection of influenza A virus and SARS-CoV-2: A retrospective cohort study.

The coronavirus 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread across the world and is responsible for over 1,686,267 deaths worldwide. Co-infection with influenza A virus (IFV-A) during the upcoming flu season may complicate diagnosis and treatment of COVID-19. Little is known about epidemiology and outcomes of co-infection. Data for 213 COVID-19 patients treated at Tongji Hospital in Wuhan from January 28, 2020 to March 24, 2020 were retrospectively analyzed. Ninety-seven of the patients (45.5%) tested positive for anti- IFV-A immunoglobulin M antibodies. The clinical characteristics were described and analyzed for patients with SARS-CoV-2 infection only and patients with SARS-CoV-2/IFV-A co-infection. Patients with co-infection showed similar patterns of symptoms and clinical outcomes to patients with SARS-CoV-2 infection only. However, an increased expression of serum cytokines (interleukin-2R [IL-2R], IL-6, IL-8, and tumor necrosis factor-α) and cardiac troponin I, and higher incidence of lymphadenopathy were observed in patients with SARS-CoV-2 infection only. Male patients and patients aged less than 60 years in the SARS-CoV-2 infection group also had significantly higher computed tomography scores than patients in co-infection group, indicating that co-infection with IFV-A had no effect on the disease outcome but alleviated inflammation in certain populations of COVID-19 patients. The study will provide a reference for diagnosing and treating IFV-A and SARS-CoV-2 co-infection cases in the upcoming flu season.