Authored by the Central Coordination Office for Prevention and Control of Infections and Antimicrobial Resistance of Grupo Luz Saúde The most common viral respiratory infections are: Influenza : a seasonal illness, primarily caused by variants of the influenza A virus. In particular, the H1N1 strain was responsible for the 2009 influenza pandemic; COVID-19 : caused by the SARS-CoV-2 virus, responsible for the recent years pandemic. This virus mutations have led to new strains, variants and subvariants, with variable transmissibility and aggressiveness; Respiratory syncytial virus (RSV) : a common cause of respiratory infections, especially in children, but also in some adults, as has been the case in the last year; Colds : caused by several respiratory viruses. Due to the low severity of the disease, these are generally not tested. Remember... Keep your flu and COVID-19 vaccinations up to date, especially if you belong to a risk group. Our Health Guide contents have an information purpose, are intended for the general public and may not be up to date. They do not substitute the individual information, opinion and advice from a doctor or other healthcare professional in each area.