# Monitoring of RSV-A and RSV-B Circulation in Poland Across Three Post-Pandemic Seasons (2022–2025)

## TL;DR

This study tracks the spread of RSV subgroups in Poland over three post-pandemic seasons, revealing shifting patterns and age-related infection trends.

## Contribution

The paper provides the first molecular-level analysis of RSV-A and RSV-B circulation in Poland after the pandemic.

## Key findings

- RSV-A and RSV-B showed equal prevalence in 2022/23, but RSV-A and RSV-B alternated dominance in subsequent seasons.
- RSV-A infections were more common in younger individuals, while RSV-B was more prevalent in adults.
- Coinfections with both RSV subgroups increased over time and were more frequent in women.

## Abstract

Respiratory syncytial virus (RSV) is a significant cause of respiratory infections across all ages. However, data on the circulation of its antigenic subgroups, RSV-A and RSV-B, remain limited in certain regions, including Poland. Therefore, this study provides the first molecular insight into the post-pandemic circulation of RSV subgroups in Poland. We analyzed 377 RSV-positive respiratory samples collected across Poland during three consecutive seasons (2022/23, 2023/24, and 2024/25) using qRT-PCR to determine subgroup distribution. An equal prevalence of RSV-A and RSV-B was observed in 2022/23, followed by RSV-A predominance in 2023/24 and a shift to RSV-B dominance in 2024/25. Individuals infected with RSV-A were significantly younger than those infected with RSV-B, a pattern evident in the latter two seasons but not in 2022/23. In general, adults (≥18 years) had higher odds of RSV-B infection (OR = 2.35, 95% CI: 1.44–3.84; p = 0.006). Coinfections with both subgroups increased from 5% in 2022/23 to approximately 15% in later seasons, and were more frequent in women. Coinfections with influenza viruses or SARS-CoV-2 were infrequent and showed no statistically significant differences between seasons. The findings of the present study highlight dynamic, region-specific RSV epidemiology and underscore the importance of sustained molecular surveillance to inform public health preparedness and guide emerging RSV immunization strategies in Poland.