Flu and RSV Cases hit All-time Low

Typically, a large group of infants and young children with no immunity to RSV would signal that when the virus returns, it will do so with a vengeance. Photo: Michal Bar Haim

PARK CITY, Utah. —For once in this past year, what’s astounding doctors is the lack of hospital visits due to infection. There have been zero hospitalizations at Intermountain Primary Children’s Hospital for children infected by RSV or the flu this year. 

“Normally, we average about 80 [cases of RSV] a week. In a really bad year, that may be 120 hospitalizations a week, and about a third of the kids that come to the hospital end up in the intensive care unit,” said Dr. Andrew Pavia, chief of pediatric infectious disease at University of Utah Health and director of epidemiology at Intermountain Primary Children’s Hospital. “This is truly remarkable.”

RSV is a common respiratory virus that causes infection in the lungs and breathing passages. Symptoms are mild and cold-like for most people, but RSV is often more severe for babies and young children as it is the leading cause of bronchiolitis and pneumonia.  

The flu is a similar story. The CDC has only 1,400 confirmed cases of the flu. That number at this time of year is typically in the 500,000 range, said Pavia. There has only been one child hospitalized for influenza in Utah this season. 

“Masking, handwashing, and physical distancing clearly played a major role, but it is hard to understand why RSV just did not show up at all this year,” Pavia said. “It’s a silver lining of the pandemic, but also a bit of a mystery.” 

The flu typically moves to the southern hemisphere in our summer and is brought back to the US. Travel restrictions have likely helped keep the flu virus from spreading internationally. But RSV stays in the US all year round. So, the non-existence of RSV is hard to understand, said Pavia. 

Unfortunately, this doesn’t mean RSV and the flu are gone for good. It could be the opposite. 

“It’s very likely when both flu and RSV have been away for a while you have more people fully susceptible to it, so when it arrives, it spreads more dramatically, and we see more severe disease,” said Pavia. 

In western Australia, where Covid-19 restrictions have let up due to the country’s successful control over the virus, there is currently a huge surge in RSV. The numbers are higher than typical years, and case numbers are spiking in the Australian summer, which is unheard of. The reemergence of RSV here could be in summer, next winter, or in another year. It’s hard to make predictions, Pavia said. 

“RSV is going to do something very strange when it comes back. We really can’t predict it very well,” said Pavia. “Our gut feeling is it’s going to come back roaring, and it will be a bad RSV year when it comes back.”