LAUSR

Coronavirus disease 2019 (COVID-19), a new, infectious, pneumonia-like disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has continued to spread rapidly worldwide, even in 2021. The COVID-19 outbreak has brought about some changes in influenza and respiratory syncytial virus (RSV) and rhinovirus infections, which were previously the main causes of viral pneumonia. This review discusses the epidemiology of these infectious diseases during the COVID-19 pandemic. Although influenza cases have been substantially decreasing worldwide, RSV infection cases, which had temporarily decreased initially, have started to increase again, and rhinovirus infection cases have been reported to be higher than usual. The authors reviewed the viral interferences among these infections in detail because they could exert considerable effect on epidemiological surveillance data. Based on experimental data, a recent study suggested that the influenza virus could promote SARS-CoV-2 infectivity. A previous study reported that influenza A virus inhibits RSV replication in an animal model. Another recent study revealed that although the replication of rhinovirus is not affected by SARS-CoV-2, the replication of SARS-CoV-2 is inhibited by rhinovirus, indicating that rhinovirus infection protects against SARS-CoV-2. Further studies are required to confirm these findings and evaluate the impact of SARS-CoV-2 on the activity of these viruses.