From the Guidelines
RSV (Respiratory Syncytial Virus) typically occurs during the fall, winter, and early spring months, with peak season generally running from mid-December to early February in the Northern Hemisphere, as indicated by the most recent study 1. The specific timing can vary by geographic location, with southern states often experiencing earlier RSV seasons than northern regions.
- RSV prophylaxis with palivizumab (Synagis) is indicated during these high-prevalence months for high-risk infants, including premature infants (especially those born before 29 weeks), infants with chronic lung disease, hemodynamically significant congenital heart disease, or other immunocompromising conditions.
- The prophylaxis is typically administered monthly throughout the RSV season, with the first dose given before the season begins, as recommended by the American Academy of Pediatrics 1. This timing is crucial because RSV is highly contagious and can cause severe lower respiratory tract infections in vulnerable populations.
- The seasonal pattern of RSV is related to environmental factors that favor viral transmission, including people spending more time indoors in close contact during colder months.
- Administration of more than 5 monthly doses of palivizumab is not recommended within the continental United States, as 5 monthly doses will provide more than 6 months of protective serum palivizumab concentrations for most infants 1.
- Children who qualify for 5 monthly doses of palivizumab prophylaxis should receive the first dose at the time of onset of the RSV season, which typically begins in November or December and ends by late March or April 1.
From the FDA Drug Label
In the northern hemisphere, the RSV season typically commences in November and lasts through April, but it may begin earlier or persist later in certain communities.
The time of year when Respiratory Syncytial Virus (RSV) is most commonly indicated is typically from November to April in the northern hemisphere, but it may vary in certain communities. 2
From the Research
Seasonality of Respiratory Syncytial Virus (RSV)
- RSV infections typically peak in the winter in temperate climates and during the rainy season in tropical climates 3.
- In the United States, RSV epidemics usually peak in December or January, but the COVID-19 pandemic disrupted this pattern during 2020-2022 4.
- A study analyzing data from 137 global locations found that RSV activity consistently peaked during winter months in temperate locales, while there was greater diversity in the tropics 5.
- In Western Australia, RSV and bronchiolitis epidemics showed clear winter peaks in July or August in temperate regions, but less identifiable seasonality in tropical regions 6.
- A retrospective analysis of respiratory tract samples found that most RSV infections were detected in the winter and early spring months, from December to March, with occasional cases throughout the year 7.
Regional Variations
- RSV epidemics began earlier in Florida and the Southeast and later in regions further north and west in the United States 4.
- A study found that 80% of tropical locations experienced distinct RSV seasons lasting 6 months or less, while the percentage was 50% for influenza 5.
- Regional differences in disease transmission dynamics and attack rates may contribute to variations in RSV seasonality 5.