RSV Season Has Started, and This Year Could Be Different

Lisa O'Mary

September 07, 2023

An increase in cases of respiratory syncytial virus in Florida and Georgia signals that RSV season has begun. 

The CDC issued a national alert to health officials Tuesday, urging them to offer new medicines that can prevent severe cases of the respiratory virus in very young children and in older people. Those two groups are at the highest risk of potentially deadly complications from RSV.

Typically, the CDC considers the start of RSV season to occur when the rate of positive tests for the virus go above 3% for 2 consecutive weeks. In Florida, the rate has been around 5% in recent weeks, and in Georgia, there has been an increase in RSV-related hospitalizations. Most of the hospitalizations in Georgia have been among infants less than a year old.

'Historically, such regional increases have predicted the beginning of RSV season nationally, with increased RSV activity spreading north and west over the following 2-3 months,' the CDC said.

One of the complications of RSV is bronchiolitis, which is the narrowing of small airways in the lungs due to swelling. Bronchiolitis results in wheezing. Most children have been infected with RSV by the time they are 2 years old. Historically, up to 80,000 children under 5 years old are hospitalized annually due to the virus, and between 100 and 300 die from complications each year. 

Those figures could be drastically different this year because new preventive treatments are available.

The CDC recommends that all children under 8 months old receive the newly approved monoclonal antibody treatment nirsevimab (Beyfortus). Children up to 19 months old at high risk of severe complications from RSV are also eligible for the single-dose shot. In clinical trials, the treatment was 80% effective at preventing RSV infections from becoming so severe that children had to be hospitalized. The protection lasted about 5 months.

Older people are also at a heightened risk of severe illness from RSV, and two new vaccines are available this season. The vaccines are called Arexvy and Abrysvo, and the single-dose shots are approved for people ages 60 years and older. They are more than 80% effective at making severe lower respiratory complications less likely.

Last year's RSV season started during the summer and peaked in October and November, which was earlier than usual. There's no indication yet of when RSV season may peak this year. Last year and throughout the pandemic, RSV held its historical pattern of starting in Florida.


CDC: 'Increased Respiratory Syncytial Virus (RSV) Activity in Parts of the Southeastern United States: New Prevention Tools Available to Protect Patients,' 'Use of Nirsevimab for the Prevention of Respiratory Syncytial Virus Disease Among Infants and Young Children: Recommendations of the Advisory Committee on Immunization Practices – United States, 2023.'


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