FRIDAY, April 7, 2023 (HealthDay News) – The typical timing of seasonal respiratory syncytial virus (RSV) epidemics (October to April) was disrupted during the COVID-19 pandemic, according to research published in the April 7 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Sarah Hamid, Ph.D., from the CDC in Atlanta, and colleagues characterized U.S. RSV seasonality during the prepandemic and pandemic periods using polymerase chain reaction test results reported to the National Respiratory and Enteric Virus Surveillance System (July 2017 to February 2023).

The researchers found that RSV circulation was historically low during the 2020 to 2021 season. During the 2021 to 2022 season, RSV began earlier and continued longer than during prepandemic seasons. A return toward prepandemic seasonality began in the 2022 to 2023 season, which started later than the 2021 to 2022 season but earlier than prepandemic seasons. In 2022 to 2023, RSV onset occurred in June and positive PCR results peaked in November. Compared with prepandemic seasons, the peak was higher (19 percent versus range of 13 to 16 percent) in the 2022 to 2023 surveillance year, with the epidemic lasting 32 weeks.