Data extraction
For each study, the following information was extracted: the author’s last name; year; country; number of patents got co-infected with SARS-COV-2 and IAV; study design; selected clinical data (age; gender; comorbidities; date of symptom onset; date of admission to hospital; days in hospital; symptom before admission; lymphocyte count on admission; oxygen saturation on admission; the first radiological images after admission; treatment; clinical events: acute liver injury, acute respiratory distress syndrome , noninvasive ventilation ,endotracheal intubation, intensive care unit (ICU); clinical ending: death or discharged). Patients were divided into moderate type (fever, cough and other symptoms are presented with pneumonia on chest CT scans) and severe type (severe type was defined if one of the following conditions was met: a. respiratory distress, respiratory rate ≥ 30 per min; b. oxygen saturation on room air at rest ≤ 93%; c. partial pressure of oxygen in arterial blood / fraction of inspired oxygen ≤ 300 mmHg) according to the Diagnosis and Treatment of Protocol of COVID-19 (National Health Commission, 2020).