The 2024-2025 Respiratory Virus Season: What to Expect

Understanding respiratory virus season forecasts is an ever-present need for clinical and research laboratories so they can appropriately prepare for the potential severity and impact of these viruses. Let’s examine what researchers are anticipating for this upcoming season, with a focus on influenza, SARS-CoV-2, and respiratory syncytial virus (RSV).

Predictive Patterns in the Southern Hemisphere 

The Southern Hemisphere’s viral patterns are a helpful indicator for the potential impact of seasonal illnesses in the Northern Hemisphere. As per the CDC, the flu season in this part of the world was largely similar to those in recent years.¹ Some highlights from their report include:

• High influenza A (H3N2) prevalence in South America.
• Influenza A (H1N1) has been predominant in Africa, but with low to moderate infection rates in most African countries.
• In Oceania, influenza A (H3N2) was the most dominant.

It should be noted, however, that variations in predominant strains and differing levels of population immunity can affect the predictive power of the Southern Hemisphere’s respiratory virus season.

What the CDC is Expecting

Based on Southern Hemisphere data, it is anticipated that this year’s respiratory virus season will closely reflect the impact and severity of last season, with the peak hospitalization rate estimated to be approximately 20 of every 100,000 individuals. 

Factors which may affect this predicted outcome may include:

• A new SARS-CoV-2 variant with pronounced existing immunity evasion
• Low vaccine uptake or effectiveness against existing strains
• Potential influence of a more severe influenza subtype

Prevalence Rates So Far

While it’s still too early to consider current prevalence rates as belonging to “respiratory virus season,” these are the trends as they are currently appearing:

• SARS-CoV-2 rates are just coming off of the highest peak of the year since January.²
• RSV cases are on the rise.³
• Influenza rates thus far remain low across the United States.⁴

For up-to-date information, the furnished links provide interactive charts to make moment-to-moment case tracking easy to access.

Changes to the Influenza Vaccine

For the 2024-2025 flu season, the CDC has recommended that the U.S. transition from the currently-used quadrivalent vaccine to the trivalent vaccine, which covers one influenza A (H1N1) virus, one influenza A (H3N2) virus, and one influenza B/Victoria lineage virus.⁵ This reflects the removal of the influenza B/Yamagata lineage virus, which has not been detected since before March 2020. 

Vaccination Support

While the government’s Bridge Access Program, which was used to provide free vaccinations to many Americans, has ended, the CDC has recently announced that they will be providing $62 million to states to help furnish free COVID-19 vaccines to low-income patients. 

Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, offers guidance on obtaining the assistance, “I would encourage folks to be reaching out to their local public health departments, their state health departments, but in addition, their federally qualified health centers as well.”⁶

The Verdict

As the lab community approaches the 2024-2025 respiratory virus season, staying informed on public health data continues to be of eminent importance. While past seasons and Southern Hemisphere trends can serve to set general expectations, respiratory viruses are by their nature unpredictable, which makes it important to stay vigilant, always learning, and adaptable. 

References:

1. Southern Hemisphere 2024 flu season update. Centers for Disease Control and Prevention. Published August 26, 2024. https://www.cdc.gov/flu/spotlights/2023-2024/southern-hemisphere-flu.htm
2. CDC. COVID Data Tracker. Centers for Disease Control and Prevention. Published March 28, 2020. https://covid.cdc.gov/covid-data-tracker/#trends_weeklydeaths_testpositivity_00 
3. RSV-NET. Respiratory Syncytial Virus Infection (RSV). Published August 30, 2024. https://www.cdc.gov/rsv/php/surveillance/rsv-net.html 
4. Weekly US Influenza Surveillance Report: Key Updates for Week 36, ending September 7, 2024. FluView. Published September 13, 2024. https://www.cdc.gov/fluview/surveillance/2024-week-36.html
5. Trivalent influenza vaccines. Centers for Disease Control and Prevention. Published March 14, 2024. https://www.cdc.gov/flu/prevent/trivalent.htm#  
6. Goodman B. Free Covid tests, treatments will return to help the country cope over fall and winter, US officials announce. CNN. August 23, 2024. Accessed September 23, 2024. https://www.cnn.com/2024/08/23/health/free-covid-tests-treatments-2024