Norovirus Signals Surge in Northern San Francisco Neighborhoods, Wastewater Data Shows

Wastewater sensors along the western side of San Francisco registered high norovirus concentrations in mid-March, part of a regional surge that WastewaterSCAN data showed extending through Central Marin County, Novato, Palo Alto, and Sunnyvale. The eastern side of the city showed moderate levels, as did Redwood City and San Jose, according to WastewaterSCAN figures reported by SFGate.

The signals built on a spike that state wastewater monitoring documented in late January, when analysis of 57 surveillance sites showed the virus surging dramatically in the Bay Area and the Los Angeles area. By mid-March, the state system also recorded high detection in Novato, San Rafael, Fremont, and Davis, with activity spreading into Los Angeles and Riverside County.

Dr. Monica Gandhi, an infectious disease specialist at UC San Francisco, pointed to a familiar weak point in containment efforts. "It is extremely contagious," she told SFGate, "and people don't wash their hands, especially kids."

That contagiousness has a potential structural explanation. Lee-Ann Jaykus, a professor in the Department of Food, Bioprocessing and Nutrition Sciences at North Carolina State University, told Newsweek that the virus periodically resets the population's immunity. "When new strains emerge, people are exposed to a strain that they have not previously been exposed to, and hence are more likely to get infected," Jaykus said. "Historically, new strains emerge every seven to 10 years, and we were due for one, so this is not surprising."

The virus, sometimes called "winter vomiting disease," typically produces symptoms within 12 to 48 hours of exposure, according to the CDC. Those symptoms include vomiting, diarrhea, stomach cramps, fever, headache, and body aches. Dehydration is the main complication, particularly for young children and elderly adults; health officials recommend electrolyte beverages or oral rehydration drinks in more severe cases.

Norovirus spreads through contaminated food and surfaces as well as direct contact with infected people. The CDC flags raw shellfish, oysters in particular, as a known carrier. Crowded environments accelerate transmission: CBS News reported that more than 150 people aboard a Princess cruise ship became infected last week out of roughly 7,000 passengers and crew on a voyage out of Fort Lauderdale sailing through the Caribbean.

For households managing exposure, health officials stress that soap and water is essential because hand sanitizer alone does not reliably neutralize norovirus. Anyone who is sick should not prepare food or care for others. Running dishes through a dishwasher's sanitizing cycle, which reaches 140 to 160 degrees Fahrenheit, is the most reliable way to decontaminate utensils and plates. WastewaterSCAN's public dashboard allows residents to track detection levels at local treatment plants as conditions continue to develop.