A public health overview shows human metapneumovirus (HMPV), a respiratory virus with no vaccine or specific antiviral treatment, detected at higher levels in wastewater across parts of California, including Merced, Novato, and Sunnyvale, with detections also reported in Los Angeles County.

There are no vaccines for HMPV, and diagnosis requires laboratory testing; most people recover with rest and fluids, while some cases may require hospital care with supportive treatments such as oxygen, anti-inflammatory steroids, or IV fluids.

HMPV is causing cases in states like California and New Jersey, with no vaccine or specific antiviral treatment currently available; care is supportive and centers on symptom management.

Credit for the reporting goes to Fernando Cervantes Jr. of USA TODAY.

Experts say prior exposure to common respiratory viruses granted some natural immunity before the pandemic, but immunity waned during periods of reduced social contact, contributing to renewed circulation of HMPV as activities resumed.

CDC prevention guidance emphasizes regular handwashing, cleaning surfaces, staying home when ill, and transmission via direct contact, sneezing, coughing, or contaminated surfaces.

Prevention also focuses on avoiding touching the face, keeping distance from sick individuals, and reducing exposure to infected droplets.

Additional CDC recommendations include thorough hand washing, avoiding face touching, staying away from the sick, cleaning frequently touched surfaces, improving indoor air quality, and covering coughs or sneezes.

HMPV was first identified in 2001 but has circulated since the 1970s, and ongoing surveillance highlights its public health impact and potential for coinfection with other respiratory viruses.

WastewaterSCAN analyzes sewage samples to detect infectious diseases and inform public health responses at multiple levels.

Symptoms are hard to distinguish from other respiratory illnesses; diagnosis relies on medical tests to differentiate HMPV from flu or COVID-19, which have their own antivirals.

Nationally, HMPV cases have been trending up since late 2025, with the virus typically circulating in winter and spring and contributing a notable share of respiratory infections during late winter to early spring.