Norovirus, a stomach bug that causes vomiting and diarrhea, is spreading fast through San Francisco.
The virus surges every winter, but this year’s outbreak is the biggest in 10 years nationally. The variant driving the current spike (GII.17) is relatively new — it first emerged about 10 years ago.
“People don’t have a lot of immunity to that norovirus,” said Dr. Peter Chin-Hong, an infectious disease physician at UCSF. “Last year we had a spike too, but this year it’s more than double that.”
WastewaterSCAN data from San Francisco’s two sewage plants show spikes in the virus far above readings at the same time last year.
Hand sanitizer doesn’t kill norovirus. If you suspect somebody in your household has the virus, bleach all surfaces they’ve touched and don’t let them prepare food for two days after the symptoms subside. Norovirus can live on surfaces like kitchen counters for up to a week.
Most people who catch the virus will feel terrible for a day or two and then recover, Chin-Hong said. Children and older people face a greater risk, as they’re more susceptible to the dangers of extreme dehydration. About 900 people nationwide die of norovirus every year, most of them elderly, according to the Centers for Disease Control and Prevention.
Spikes generally occur in the winter because more people are together indoors, sharing mugs, dishes, and cutlery. Norovirus isn’t respiratory like Covid or the flu — rather than breathing it in, you have to eat it in order to become infected. And in most cases, Hong-Chin said, this happens after people touch an infected surface, then touch their mouths.
“It’s very hardy,” Chin-Hong said. “You have to wash your hands with soap and water.”
San Francisco’s Department of Public Health confirmed wastewater data has shown high levels of norovirus this winter, adding that the department does not have case data for the virus. The department advised that, in addition to frequent handwashing and cleaning surfaces, people could avoid norovirus by carefully washing fruits and vegetables before eating them.