Seasonal respiratory virus trends in pediatric patients during the COVID-19 pandemic in Brazil.

Acute respiratory infections are a constant public health problem causing childhood morbidity and mortality worldwide. Reported cases of major respiratory infections decreased in 2020 after restrictive measures were adopted to contain the COVID-19 pandemic, but there is little data on the impact after these measures were relaxed in the subsequent years. This study conducted molecular analysis to identify rhinovirus, respiratory syncytial virus, influenza A virus, and adenovirus in SARS-CoV-2-negative samples taken from symptomatic pediatric patients during 2021 and 2022 to ascertain the impact of pandemic response measures within the broader epidemiological scenario. The positivity rates found were 28.3% and 50.8%, in 2021 and 2022, respectively, representing a significant increase (1.8 times) in the circulation of non-SARS-CoV-2 viruses after the reduction of non-pharmacological measures to contain the COVID-19 pandemic. Within the positive samples, rhinovirus and respiratory syncytial virus were most frequent (44.4 and 18% in 2021; 44.5 and 22.5% in 2022), whereas influenza A and adenovirus were found in lower frequency (12.5 and 5.5% in 2021; 13.4 and 4.9% in 2022, respectively). Because these different respiratory virus diseases produce similar symptoms, diagnosis based on clinical condition alone can be inaccurate, and more reliable testing is required to select the best therapeutic approach for each case. The loosening of restrictive measures to contain the COVID-19 pandemic led to higher numbers of other respiratory infections in pediatric patients. Ongoing surveillance and differential diagnosis of respiratory viruses are required to better understand their seasonal patterns after the COVID-19 pandemic to guide prevention and control strategies.