Clinical characteristics and outcome of influenza virus infection among adults hospitalized with severe COVID-19: A retrospective cohort study from Wuhan, China

Background Coronavirus disease 2019 (COVID-19) is an emerging infection disease that rapidly spreads worldwide. Co-infection may occur in some cases of COVID-19, like influenza virus and so on. Clinical features and outcomes of severe COVID-19 patients with co-infection of influenza virus need to be noticed.Methods Retrospective cohort study was performed and total of 140 patients with severe COVID-19 was enrolled in designated wards of Sino-French New City Branch of Tongji Hospital between Feb 8th and March 15th in Wuhan, Hubei province, China. The demographic, clinical features, laboratory indices, treatment and outcomes of these patients were collected and analyzed.Results Of 140 severe COVID-19 hospitalized patients, 73 patients were with median age of 66 years old with identification of influenza virus IgM-positive and 67 patients were with median age of 62 years old in influenza virus IgM-negative. Nearly half of severe COVID-19 patients in this research are male. Majority of the severe COVID-19 patients had chronic underlying conditions. Wheeze was the clinical feature of severe COVID-19 patients with influenza IgM-positive (26.4% vs 9.0%, P = 0.008). On contrary, fatigue or myalgia was the feature of the COVID-19 patients without IgM-positive (38.4% vs 58.2%, P = 0.019). Increased levels of ferritin and prolonging APTT were showed in severe COVID-19 patients without influenza IgM-positive compared with patients in other group with significant differences. Death rate in the group of severe COVID-19 patients with influenza IgM-positive is lower than it in other group with significant differences (4.1% vs 14.9%, P = 0.040). In univariate regression analysis, several factors were associated with higher risk of death, which included LDH, troponin, NT-proBNP, D-dimer, PT, APTT, lymphocytes, platelet and eGFR. However, influenza virus IgM positive was associated with lower risk of death.Conclusions Characteristic features of patients with severe COVID-19 with influenza virus IgM-positive were described. Co-infection may occur during the pandemic of COVID-19, and we need to improve our understanding in order to confront this crisis in the future.