A virus that isn’t COVID or the flu is pummeling Northern California

Human metapneumovirus, or HMPV, typically spreads during winter and spring

Downtown San Francisco skyline. HMPV is surging in parts of the Bay Area, wastewater data shows.

Vadym Terelyuk/Getty Images

If you notice that your office is emptying out, chances are it’s because a respiratory virus that few people have actually heard of is circulating throughout Northern California.

According to recent WastewaterSCAN data, concentrations of human metapneumovirus, or HMPV, are high in San Francisco, Marin, Vallejo, Napa, Novato, Santa Rosa, Sacramento and Davis. The respiratory illness, which typically lasts from winter through spring, causes familiar symptoms like cough, fever and congestion, and spreads through contaminated surfaces, the air and person-to-person contact. The Centers for Disease Control and Prevention says that the virus leads to mild illness in healthy children, but can also cause less-common symptoms like bronchiolitis — an infection of the airways — and croup, described as a “barking” cough. The distinct cough, which the Mayo Clinic describes as similar to a seal barking, is most common among small children.

Dr. Monica Gandhi, an infectious disease specialist at UC San Francisco, said that because COVID-19 was “quieter” this season, “other viruses like influenza and HMPV are getting their chance.”

These illnesses “compete with each other,” she explained to SFGATE on Monday. “When we had big COVID surges, we saw really low rates of other common cold viruses.”

Data shows an upward trend of HMPV throughout the U.S., according to the Centers for Disease Control, and WastewaterSCAN data shows that the Midwest and Northeast are experiencing the highest rates of the virus. This is because HMPV is an RNA virus, a type of virus that also includes COVID-19 and typically thrives in cold environments. As people crowd together indoors, the virus spreads much more rapidly, Gandhi explained. In California, however, mild weather and consistent ventilation can help keep them at bay.

To prevent spreading HMPV to others, the CDC recommends staying home when sick, washing your hands and regularly cleaning surfaces. There are no specific treatments or vaccines to cure or prevent HMPV. Most people will recover if they stay home to rest and recover and drink lots of fluids, according to the CDC.