Not many people had heard of human metapneumovirus, or HPMV, until a surge of recent cases in China made headlines.

In actuality, the seasonal virus is so common that most people, including U.S. residents, have had HPMV without knowing it, Northeastern health experts say.

"It's a respiratory illness that can cause common cold symptoms like cough, runny nose and sore throat," says pharmacy professor Brandon Dionne.

"It's a common virus that's been part of the normal respiratory viral season for years," he says. "It follows the same kind of pattern as our other respiratory viral infections like RSV and flu."

"This is not something new," says Neil Maniar, director of Northeastern's master of public health program. "It's not the next COVID-like pandemic or anything like that."

"The data suggest that by the time you are 5 or 6 years old, pretty much everybody's had it (HMPV)," says Samuel Scarpino, an epidemiologist and Northeastern professor of the practice in health sciences and computer sciences.

"Pretty much everybody (gets it) as they go through childhood," he says.

Scarpino, who is also director of AI + Life Sciences at Northeastern, calls HMPV "an understudied disease we don't often test for."

That changed in China when the country started testing for -- and detecting -- cases of HMPV.

"A few weeks ago, China said it was rolling out a new surveillance system for pneumonia of unknown origin," Scarpino says.

"They're claiming -- and this seems plausible -- that they're catching a lot of human metapneumovirus cases. They stepped up surveillance, and as a result have caught more cases because they are now looking for them," he says.

"This is something that folks are going to watch closely in the global health community, but it is not setting off alarm bells the way it was for COVID," Scarpino says.