2.3 Virus identification
H1N1 virus infection were confirmed by analysis of nasopharyngeal swabs, sputum, bronchoalveolar lavage fluid and/or blood and/or urine samples using H1N1 virus Nucleic Acid Detection kit (Liferiver)22. SARS-CoV-2 infection were confirmed by analysis of nasopharyngeal swabs, sputum and blood samples using nucleic acid detection by RT-PCR23.