RSV season stretches into spring, prompting some regions to extend immunization window

WASHINGTON — The rate of RSV cases remains higher than normal for this time of year, stretching the respiratory illness season later into spring. That’s why many regions across the U.S. are opting to extend the window for immunizations through the end of April. 

Respiratory syncytial virus, or RSV, normally follows a fall-to-spring pattern with a peak during the winter. Immunizations are typically recommended through the end of March to correlate with the season, which can vary by region. This season has shifted, however, with federal data showing positivity rates that are significantly higher than they were this time last year. 

The extension means providers can continue to offer protection for a longer period, which health experts say is critical. RSV remains the leading cause of infant hospitalization. 

According to the U.S. Centers for Disease Control and Prevention, cases of RSV began to spread later than expected, leading the agency to believe the virus could continue to spread into late April in many regions. 

A report from the Association of Immunization Managers published in early April indicates that 48 of the 66 federally-funded immunization programs across the U.S. are extending their seasons through April 30. 

The CDC said that despite the shift in the season length, the severity remains comparable to previous years. 

While it’s unclear why the virus is sticking around later in the spring, doctors say continued access to immunization could make a real difference. 

Respiratory syncytial virus is a highly contagious respiratory illness that spreads easily, typically by coughing or sneezing or other direct contact with a person who has it. 

Symptoms are generally mild and may present similar to a cold, but it can cause severe illness. Infants, young children and adults who are older or who have certain risk factors are at higher risk of developing severe illness. 

Cases are most common from fall to spring, with illnesses peaking in the winter. 

People with RSV who are otherwise considered healthy are typically contagious for three to eight days, even if symptoms are not present. However, according to the CDC, some infants and people with weakened immune systems can spread the illness for four weeks or longer, even if they’re not showing symptoms. 

Two to three out of every 100 infants under 3 months are hospitalized with RSV every year, according to the CDC. 

CNN Newsource contributed to this report.