A respiratory virus has been spreading in several states that isn’t the flu or a cold.
The Centers for Disease Control and Prevention said the number of cases of human metapneumovirus has been growing since the start of winter.
USA Today reported that California and New Jersey have seen an uptick in HMPV.
The last spike in cases came in April 2025. The latest data shows it is about 5% of positive tests for respiratory viruses as of Feb. 21. The week prior, the percentage was 3.83%. In April 2025, HMPV accounted for about 7.43% of respiratory illness cases, the National Respiratory and Enteric Virus Surveillance System, or NREVSS said.
Influenza, for comparison, is 17,91% of respiratory cases for Feb. 21, RSV is 8.62% and COVID is 4.29% of cases.
There has been an increase in positive tests for HMPV in New Jersey, while the number of flu cases fell, the New Jersey Department of Health said.
HMPV has been found in wastewater in California, according to The Sacramento Bee. The newspaper said there were high concentrations of the virus in Sacramento, Davis, San Francisco, Marin, Vallejo, Napa, Novato and Santa Rosa, according to data collected by WastewaterSCAN.
Cases are also popping up in the Los Angeles area, the Desert Sun reported.
What is HMPV?
The CDC said that the illness, also known as HMPV, can cause respiratory illness in people of all ages and can cause a mild illness in healthy children.
WebMD says it is very common.
It was first discovered in 2001 and is part of the Pneumoviridae family. While it was only discovered about 25 years ago, it’s been the source of infections globally for more than 50 years, according to WebMD.
Most people have had it by the age of 5 and you can get it multiple times.
Those most at risk are under the age of 5 and older than 65, as well as people with a weakened immune system and people with asthma or chronic obstructive pulmonary disease, according to the Cleveland Clinic.
Typically, it spreads in the winter and lasts through spring, the CDC said.
Prevention, such as hand washing, cleaning surfaces and staying home when sick, are keys to not getting the illness, especially since there is no treatment.
It spreads from person to person or surface to person, the CDC said.
The symptoms are similar to the common cold, the Cleveland Clinic said.
Symptoms include:
- Cough
- Fever
- Nasal congestion
- Shortness of breath
- Sore throat
- Wheezing
- Rash
In some cases, it can progress into bronchitis or pneumonia, according to the Cleveland Clinic.
Other complications may include bronchiolitis, asthma flare-ups, COPD flare-ups and ear infections.
Since there is no treatment, the CDC says that if you get the virus, the best thing to do is to drink plenty of liquids and stay home and rest while it runs its course.
Severe cases may need oxygen, IV fluids or corticosteroids.
Antibiotics don’t work since they are to combat bacteria, and HMPV is a virus, the Cleveland Clinic said. Sometimes, however, a person can have both the virus and a secondary infection, where an antibiotic may be prescribed.
Typically a HMPV illness can last a few days to a week, but it may take longer if the illness is severe and some symptoms may stick around, like a cough, according to the Cleveland Clinic.
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