Delayed RSV season in WA keeps rates elevated, with infant hospitalizations highest

OLYMPIA, Wash. (KATU) — Parents and caregivers in Washington state will have an extra month to get respiratory syncytial virus (RSV) protection for infants this season as health officials say the virus is still circulating at elevated levels later than usual.

The Washington State Department of Health has extended the availability of RSV immunizations for infants through April 30.

RSV immunizations are typically available between October and March, but the department said disease activity remains elevated across the state.

“Our hope is that by extending the administration period for RSV immunizations, we can continue to keep babies out of the hospital while disease activity is still high,” said Dr. Tao Sheng Kwan-Gett, the state health officer at the Department of Health.

“If you have an infant younger than 8 months or a higher-risk toddler between 8 and 19 months old who hasn’t gotten immunized against RSV this season, talk to your child’s health care provider as soon as you can about RSV protection.”

RSV is a common respiratory virus that usually causes mild, cold-like symptoms, but it can lead to severe illness, hospitalization and death in some groups, including infants and older adults. The Department of Health said RSV is the leading cause of infant hospitalization in the United States.

State officials said the 2025–26 RSV season in Washington started later than normal, with increased activity beginning in December—more than a month later than previous seasons.

RSV hospitalization rates among infants younger than 1 year have been the highest of any age group this season, peaking at about 26 per 100,000 in January, with rates still elevated as of late February. The delayed start and continued elevated activity into late winter are consistent with national patterns, the department said.

In an interview with KATU, Dr. Scott Lindquist said the state was first alerted to the later-than-usual season by the CDC.

“What has happened this year with the RSV season is it appears to be about a month-to-two-months later than usual,” Lindquist said, adding that the extension is tied to continued activity past March. He said the reason for the delayed timing is unclear.

“No one really understands this,” he said.

Lindquist, the medical state epidemiologist for the state of Washington, said infants and toddlers are especially vulnerable because the virus can affect their airways and cause significant breathing problems.

He said RSV can come in “really intense bursts during the respiratory season,” and some children are more prone to severe illness, including younger children and those with underlying lung conditions.

RSV can spread in multiple ways, including through contact.

“To be honest with you, the most common spread of RSV is your fingers,” Lindquist said. He urged what he called “respiratory etiquette,” including handwashing, covering coughs and staying home when sick, especially from work, school or day care.

For infants, RSV immunization is provided through monoclonal antibody products such as nirsevimab (Beyfortus) and clesrovimab (Enflonsia), which provide antibodies to help protect young children from RSV.

The Department of Health said protection lasts at least five months.

The department recommends that all children younger than 8 months receive nirsevimab during their first RSV season.

Children ages 8 to 19 months who are at higher risk because of medical conditions or weakened immune systems can get nirsevimab in their second RSV season.

The department also recommends nirsevimab in the second season for American Indian and Alaska Native children in that age group because they are at higher risk of severe RSV disease.

Monoclonal antibody products can be administered in birthing hospitals before discharge and in provider offices.

The Department of Health said parents and caregivers should talk with their child’s health care provider about whether RSV protection is recommended for their child.

Lindquist said vaccination rates “are not severely robust,” and pointed to confusion around immunizations.

He said the department’s message is for families to seek guidance from a trusted medical source. “If you want to get information or trusted advice, talk to your healthcare provider,” he said.

The Department of Health said more information about RSV in infants and children is available on its website.