Backgrounds:

RSV circulation was profoundly affected by the COVID-19 pandemic. The aim is to describe RSV detection in a tertiary pediatric hospital in central Portugal during this period and comparing it with previous seasons.

Methods

Retrospective analysis of all children with acute respiratory infection observed in an Emergency Service with RSV detection by PCR in nasopharyngeal samples as part of routine care, from April 2015 to December 2021. An epidemic year was defined from the April 1 to March 31 of the following year.

Results:

RSV was detected in 2662 samples. In the pre-COVID-19 era, epidemics started in November/December and peaked in December/January. Acute bronchiolitis was the most frequent diagnosis, with a median age of 8M. In 2020/21 there were no cases of RSV infection. In 2021/22 the epidemic started in May, peaking in August/September (figure) with the most frequent diagnosis being nasopharyngitis, with a median age of 21M.

Admitted patients (staying >=24h) in the current epidemic compared to the pre-COVID-19 epidemics, showed a mean age of 18M vs 12M, with a bronchiolitis diagnosis in 58 % vs 74% (p<0,05), oxygen requirement in 52% vs 69% (p<0,05), chest X-ray performed in 49% vs 56% (p=0,17), lab tests ordered in 41% vs 54% (p=0,01), antibiotic use in 29% vs 28% (p=0,805), intensive care admission in 4% vs 11% (p=0,02) and mean duration of admission of 4 vs 7 days (p<0,01).

Conclusions/Learning Points:

In 2021 we observed a big epidemic outside its usual period, with older children, predominantly with rhinopharyngitis, which may have been influenced by different testing criteria during the COVID-19 pandemic. Admitted patients had less supplemental oxygen requirement, less admission to intensive care and shorter duration of admission, which suggest a less severe disease.