Norovirus Outbreak Sweeps Across Northern California

The highly contagious 'stomach flu' virus is impacting parts of the Bay Area, including San Francisco, Marin, and Palo Alto.

Mar. 16, 2026 at 7:50pm

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A norovirus outbreak is ripping through Northern California, with dozens of people falling ill with symptoms like vomiting, diarrhea, and cramps. The virus, often referred to as the 'stomach flu' or 'winter vomiting bug', has been detected in wastewater treatment facilities across the Bay Area region. Health experts warn the virus is extremely contagious, especially in places where people congregate closely like salad bars and cruise ships.

Why it matters

Norovirus outbreaks can have significant public health and economic impacts, causing widespread illness and disrupting businesses and travel. This outbreak highlights the need for improved hygiene practices, especially handwashing, to help limit the spread of highly contagious viruses in the community.

The details

The norovirus outbreak has been detected in parts of western San Francisco, Marin, Novato, Palo Alto, Sunnyvale, and Redwood City and San Jose. Health officials say the virus is often spread through contaminated food or surfaces, and can affect people of all ages. The outbreak comes after more than 150 people were sickened with norovirus on a recent Princess Cruises voyage in the Caribbean.

  • The norovirus outbreak was first detected in Northern California wastewater treatment facilities on Sunday, March 16, 2026.
  • The Princess Cruises outbreak occurred during a voyage from March 7 to March 14, 2026.

The players

Dr. Monica Gandhi

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

WastewaterSCAN

A program that monitors wastewater for the presence of pathogens like norovirus, which detected the virus in Bay Area treatment facilities.

Princess Cruises

A cruise line that experienced a norovirus outbreak affecting over 150 passengers and crew members on a recent Caribbean voyage.

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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)

“'[Norovirus often begins] at salad bars and cruise ships and places where people congregate closely.'”

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

The takeaway

This norovirus outbreak serves as a reminder of the importance of proper hygiene, especially handwashing, in preventing the spread of highly contagious illnesses. Public health officials will need to closely monitor the situation and provide guidance to the community on how to limit the impact of the outbreak.