Unfamiliar respiratory virus causes big problems for some

(CNN) - A little-known respiratory virus causes symptoms like the flu and COVID-19, and spiked this spring, according to numbers from the U.S. Centers for Disease Control and Prevention.

It’s also led to hospitalizations among many of the most vulnerable, like young children and seniors.

It’s called human metapneumovirus or HMPV, a virus that wreaked havoc on the U.S. this spring, filling some hospitals with young children and seniors, according to the CDC.

“The symptoms are identical almost to influenza and respiratory syncytial virus,” said Dr. Jorge Rodriguez, a board-certified internal medicine specialist.

Those symptoms include a hacking cough, runny nose, fever and shortness of breath.

At its peak in mid-March, nearly 11% of tested specimens were positive for HMPV.

“What is most concerning is the fact that it has increased approximately 36% in the last year,” Rodriguez said.

The virus has been around for a while. Health experts believe pandemic precautions, like masking, kept it at bay.

“Now that we’ve let down our defenses, now that we are not as cautious, all these viruses - think of it this way -- were just waiting to pounce, and indeed, they are pouncing,” Rodriguez said.

Most people who caught HMPV probably didn’t even know they had it.

Sick people aren’t usually tested for it outside of a hospital or emergency room.

Unlike COVID-19 and the flu, there’s no vaccine for HMPV or antiviral drugs to treat it. Instead, doctors care for seriously sick patients by tending to their symptoms.

“The best treatment is precaution and prevention,” Rodriguez said.

Health experts said that’s why it’s important to be aware of this virus, especially if those most vulnerable to it get sick.

“Monitor them,” Rodriguez said. “If they get sicker, for example, if they get short of breath or their fever spikes up above 103 or 104 (degrees Fahrenheit), then you need to go see a physician.”

Because testing for HMPV is rarely done outside hospitals, it’s hard to know the true burden of the disease.

Blood tests indicate that most children have had it by the age of 5.

A 2021 study in the Lancet Global Health estimated that among children younger than 5, there were more than 14 million HMPV infections around the world in 2018, more than 600,000 hospitalizations and more than 16,000 deaths.