After Brutal RSV Seasons, Wisconsin Hospitals See Relief

Vaccination. (Pixabay License)

Less than four years ago, hospitals in Wisconsin and across the country struggled to care for the large number of infants and young children being hospitalized with respiratory syncytial virus.

Now RSV activity is down for a second winter in a row. Some of the state’s top infectious disease experts are cautiously optimistic that access to immunizations are contributing to the declining numbers.

RSV is a common respiratory virus with symptoms similar to a cold or flu for most healthy adults and children. But the disease can be severe in infants under 6 months old and adults age 75 and older or who have certain medical conditions.

In 2023, RSV vaccines for adults and those who are pregnant, as well as monoclonal antibodies for infants and young children, were approved by the Food and Drug Administration. But due to a shortage of the monoclonal antibodies during the 2023-2024 flu season, this winter is the second season all of the immunizations have been widely available.

Tom Haupt, a respiratory epidemiologist and the influenza surveillance coordinator for the Wisconsin Department of Health Services, said RSV activity has been down across the country over the last two flu seasons. He said for epidemiologists, the trend is “surprising but also very satisfying.”

“For the past two years, RSV has not been as predominant as it has been in the past,” Haupt said. “We could average somewhere between 30 to 35 percent (test) positivity rate three or four years ago. And last year, I don’t think we even hit 10 percent.”

For the week ending on Feb. 14, less than 8 percent of people tested positive for RSV, according to DHS data.

Haupt said deaths related to RSV are also down in older adults, and the state has not seen any pediatric deaths from the virus this winter.

But he said two flu seasons do not provide enough data for public health experts to say whether the vaccines are behind the change.

“It’s a little early to make an absolute call on this, but it does look very promising,” Haupt said.

Dr. James Conway, pediatric infectious disease specialist at UW Health, cautioned that the current cold and flu season is not over yet and there could be an increase in activity in March.

But Conway said there has been a noticeable decline in the number of babies admitted to his hospital since the monoclonal antibodies became more widely adopted last year.

“I just remember vividly, standing there on the ward at the end of January last year and looking up one hallway and looking up the other hallway,” Conway recalled. “Just two years ago, a whole bunch of those rooms would have been babies with bad coughs and wheezing and having trouble feeding, all the things that RSV can do. So as we did better (rolling out the shots), we really did see a flattening out of the curve.”

Conway said he hopes fewer hospitalizations and deaths could be a “new normal” for RSV activity. But he said that future depends on the most vulnerable populations continuing to get vaccinated against the virus.

“I’d really feel terrible if a bunch of parents next year basically say, ‘Oh yeah, I guess that RSV thing went away. I can skip getting this relatively new thing for my kid,’ and lo and behold, we get a resurgence of disease,” Conway said.

Haupt said around 64 percent of eligible babies and mothers in Wisconsin were immunized against RSV during the 2024-2025 flu season. So far this winter, nearly 23,000 doses of the monoclonal antibodies have been administered, similar to last season.

The latest state data shows just under 39 percent of people age 75 and older have gotten the shot this winter.

Getting the shot to more vulnerable seniors is an important next step in continuing to fight the disease, Haupt said.

He said the few RSV deaths in the state this season have been in residents of long-term care facilities, and he’d like to see the RSV vaccine become as widely administered as the flu shot to help protect these older adults.

Listen to the WPR report

RSV cases are down. Health experts are optimistic a new vaccine is behind it was originally published by Wisconsin Public Radio.