Norovirus Outbreak Hits Northern California

Wastewater monitoring shows high levels of the contagious stomach bug in several Bay Area cities.

Mar. 16, 2026 at 4:51pm by Ben Kaplan

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Northern California is grappling with a surge in norovirus cases, a highly contagious gastrointestinal illness that causes vomiting, diarrhea, and other flu-like symptoms. Wastewater surveillance data indicates elevated levels of the virus in several Bay Area cities, including San Francisco, Marin, Palo Alto, and Sunnyvale. Health experts warn the virus can spread quickly, especially in crowded settings like cruise ships, and emphasize the importance of handwashing to prevent transmission.

Why it matters

Norovirus outbreaks can have significant public health and economic impacts, leading to widespread illness, hospitalizations, and disruptions to businesses and travel. The current outbreak in Northern California highlights the need for vigilance and effective prevention measures to control the spread of this highly contagious virus.

The details

According to WastewaterSCAN, a health organization that monitors wastewater for various viruses, including COVID-19 and norovirus, the Bay Area is currently experiencing elevated levels of the norovirus. The virus has been detected at high levels in western San Francisco, Marin, Novato, Palo Alto, and Sunnyvale, and at moderate levels in Redwood City, San Jose, and eastern San Francisco.

  • The current norovirus outbreak in Northern California began in early 2026.

The players

WastewaterSCAN

A health organization that monitors wastewater for various viruses, including COVID-19 and norovirus, to provide the public with information about disease circulation.

Dr. Monica Gandhi

An infectious disease specialist at the University of California, San Francisco, who provided expert commentary on the norovirus outbreak.

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What they’re saying

“It is extremely contagious, and people don't wash their hands, especially kids.”

— Dr. Monica Gandhi, Infectious Disease Specialist, UC San Francisco (SFGATE)

What’s next

Health officials are urging residents to take precautions, such as frequent handwashing, to prevent the further spread of the norovirus outbreak in Northern California.

The takeaway

The current norovirus outbreak in Northern California underscores the importance of maintaining good hygiene practices, especially handwashing, to control the spread of this highly contagious gastrointestinal illness. Vigilance and proactive prevention measures are crucial to mitigate the public health and economic impacts of such outbreaks.