What’s being called a “tripledemic” of respiratory viruses is hitting Utah and other parts of the country hard right now.

The trio — COVID-19, RSV or respiratory syncytial virus, and influenza — are spreading much faster than normal, doctors warn, with RSV and flu cases already filling Primary Children’s Hospital “to the brim,” delaying some surgeries and outpatient procedures. Adults, too, are being hospitalized with RSV.

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Even COVID-19 cases are once again climbing, thanks to ever more highly transmissible versions of the omicron variant that sent cases soaring to record levels last winter and forced overwhelmed hospitals to turn away some patients.

Can you catch multiple viruses at the same time?

The definition of “tripledemic” is actually pretty simple.

“We’re talking about those three viruses all circulating at higher levels than we’re used to at this stage of a respiratory season,” said Dr. Brandon Webb, an associate professor of infectious diseases with Intermountain Healthcare.

But that doesn’t mean most people are likely to get all of them all at once.

“We’re generally not talking about one individual having more than one of these viruses at the same time. It can happen, but it’s not the norm,” Webb said. “The norm is that these viruses tend to be a one-at-a-time phenomenon.”

There are exceptions, he said, especially in patients who are immunocompromised due to cancer treatments, organ transplants or underlying conditions that can be genetic. Newborns and infants also can have multiple viruses at the same time, Webb said.

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Why are RSV and the flu such a concern now?

For the past two winters, public health precautions taken during the COVID-19 pandemic helped bring RSV and the flu to nearly a standstill. But both of the sometimes deadly viruses have come back now that most people are no longer routinely wearing a mask or taking other measures that slow the spread of respiratory illnesses.

There’s also what Webb called “the immunity gap,” caused by a lack of recent exposure to the two viruses.

“What that means is that in normal circumstances, in a non-pandemic environment, these seasonal viruses spread through the community each year and they affect a wide swath of people,” Webb said, “some who have exposure but no symptoms, some who have very mild symptoms and some who have more severe symptoms.”

Each season, that allows people to develop some immunity to RSV and flu viruses, the doctor said.

“That repeated exposure, season over season, generates sort of a constant background of immunity in a population,” Webb said, although it ends up being “incomplete because immunity to respiratory viruses doesn’t last very long.”

The short-lived protection from an infection is “the same phenomenon that we’ve been frustrated with, with COVID, where the immunity wanes over time, is true for immunity to RSV and influenza, and the croup virus as well,” he said.

Still, there’s enough immunity generated overall that it “primes the pump to some degree and establishes this background level of partial immunity so less people are fully non-immune as the next wave, the next season, comes on,” Webb said.

Why this respiratory virus season is different

It’s all about the immunity gap.

“What we’re seeing this year is the consequences of having two respiratory viral seasons in a row where we had very, very low rates of RSV and influenza. So the partial immunity has waned tremendously,” he said. “Many, many people who had been exposed, or had some partial immunity in years past don’t have that anymore.”

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That lack of immunity is driving the early peaks in RSV and flu cases, Webb said.

The immunity gap has also made getting an annual flu shot even more important this year, health experts have said. There isn’t an RSV vaccine yet, but staying up to date on COVID-19 vaccinations is also recommended, including the updated booster dose targeted at omicron subvariants.

Because the viruses can cause severe disease in the very young and the very old, as well as those with certain medical conditions, Webb advised anyone with even mild cold symptoms to take precautions like wearing a mask and avoiding contact with the vulnerable.

“There’s just a lot of overlap between these virus,” the doctor said, making it difficult to know without testing if what seems like a cold is something more serious. “No matter what you’re sick with, one thing we’ve learned from the pandemic is it’s really important to protect others.”

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