Both RSV and the flu are nearly nonexistent in Utah and the rest of the country this year, Dr. Andrew Pavia, director of epidemiology at Primary Children’s Hospital, said Monday as the state reported 338 new COVID-19 cases and just one additional death from the coronavirus.

Usually at this time of year, hundreds of infants and toddlers would be hospitalized in Utah with RSV, as the respiratory syncytial virus is commonly known. But so far this winter, there has not been a single admission for the virus at Primary Children’s Hospital, and influenza infections are extremely rare.

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Public health measures taken to slow the spread of COVID-19, including travel restrictions that speed up the circulation of seasonal flu, may help account for the slowdown in flu cases, but the explanation for RSV all but going away is not as clear, Pavia said.

“Masking and physical distancing and better hand-washing, we’ve known for years can control flu. Now we’re doing this natural experiment where we’re controlling it really dramatically,” Pavia said, adding that “RSV is somewhat more perplexing” because it does no go away in the summer, like the flu.

Masking is helping, however, as well as keeping children as home during the pandemic, he said.

“But there might be some other things we don’t fully understand because all these things might be expected to drive RSV down to low numbers, but it’s practically zero across the nation,” Pavia said, adding one theory that has yet to be proven is that the COVID-19 virus has driven other viruses, like RSV, away.

The low case counts for RSV and the flu don’t mean the respiratory infections have gone away, however.

Pavia said both may hit Utahns hard, maybe even during warmer months.

“It’s very likely that 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,” he said, adding that a severe flu season usually follows one that is mild.

RSV depends on more babies “who are completely susceptible” to the virus, Pavia said, so next year, there will likely be twice as many infants who have never been exposed. He said Australia, where it’s now summer and COVID-19 restrictions have been relaxed, is now seeing a huge surge in RSV.

“Our gut feeling is it will come roaring back,” the doctor said, noting RSV affects older adults as well as the youngest children.

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COVID-19 cases are on the decline, but with the 338 new cases reported Monday have reached 367,073 since the beginning of the pandemic last March. Vaccinations appear to be helping, with 611,910 doses administered in the state, including 4,353 since Sunday.

The rolling seven-day average for positive tests is 760 per day. Another 2,892 Utahns have been tested, and an additional 5,931 tests conducted. The rolling seven-day average for percent positivity when multiple tests by an individual within 90 days are excluded is 13.3%, or 6% when all tests are included, which is now the state’s preferred method.

There are 237 people hospitalized with the coronavirus in Utah. As the national death toll nears 500,000, Utah has lost 1,853 people to COVID-19 with the latest death reported Monday, a Wasatch County woman between 45 and 64 who was a long-term care facility resident.

Correction: An earlier version of this story incorrectly referred to Dr. Andrew Pavia as Dr. Anthony Pavia.