Trending Now - Outbreak of Untreatable Virus Spreads Quickly in Western State
WHO:
Dr. Neha Nanda, chief of infectious diseases and hospital epidemiologist for Keck Medicine of USC
Dr. Jessica August, chief of infectious diseases at Kaiser Permanente Santa Rosa
Dr. Matthew Binnicker, director of the Clinical Virology Laboratory at Mayo Clinic
Dr. Monica Gandhi, infectious disease specialist at UC San Francisco
Dr. David Weber, professor and Medical Director in Infectious Diseases at UNC Health
Centers for Disease Control and Prevention (CDC)
WHAT:
A respiratory virus, human metapneumovirus (HMPV), is spreading in California.
HMPV has been detected in wastewater in Northern California communities, including Merced, Novato, Sunnyvale, Redwood City, San Francisco, Marin, Vallejo, Napa, Santa Rosa, Sacramento, and Davis.
The highest test positivity rate for HMPV in 2026 was 6.1% on February 21.
HMPV was first detected in 2001.
There is no vaccine or specific treatment for HMPV.
HMPV can lead to severe symptoms, including pneumonia, asthma attacks, and bronchitis.
An estimated 12 hospitalizations per 100,000 U.S. adults occurred annually from 2016-2019 due to HMPV.
WHERE:
California, specifically Northern California communities such as Merced, Novato, Sunnyvale, Redwood City, San Francisco, Marin, Vallejo, Napa, Santa Rosa, Sacramento, and Davis.
Nationally, HMPV levels are also rising in the Midwest and Northeast.
WHEN:
HMPV levels have been rising since October 2025.
The virus typically circulates in winter and spring.
The peak for HMPV in 2024 was 11.7% at the end of March, and in 2025, it peaked at 7.15% in late April.
WHY:
The resurgence of HMPV is attributed to a lack of natural immunity developed during the COVID-19 pandemic, as people were less exposed to seasonal viruses.
HOW:
HMPV spreads through close contact, coughing, sneezing, and touching contaminated surfaces.
Preventative measures include regular hand washing, cleaning surfaces, and avoiding contact with sick individuals.
A respiratory virus known as human metapneumovirus, or HMPV, is currently spreading in Northern California, with detections reported in wastewater across several communities, including San Francisco and Sacramento. The Centers for Disease Control and Prevention indicates that HMPV can lead to serious health issues like pneumonia and bronchitis, and while it typically circulates during winter and spring, cases have been rising since last October, with the highest positivity rate this year reaching 6.1% on February 21. Experts, including Dr. Neha Nanda and Dr. Jessica August, warn that the resurgence is likely due to reduced natural immunity from the COVID-19 pandemic, and they emphasize the importance of preventive measures like hand washing and avoiding close contact with those who are sick.