Wastewater testing has revealed parvovirus B19 circulating throughout the San Francisco Bay Area and Sacramento region, leading health officials to highlight its symptoms and heightened risks for pregnant people and those with weakened immune systems.
With flu season coming to an end, new data shows that another highly contagious virus is appearing throughout Northern California.
The parvovirus B19, often referred to as the “slapped cheek” rash for its distinctive red rash on the face, was detected in wastewater surveillance data throughout the San Francisco Bay Area and Sacramento region.
Children and adults infected with parvovirus B19 will often experience no symptoms or mild illness with flu-like symptoms, rashes and joint pain, according to the Centers for Disease Control and Prevention. The illness usually goes away in seven to 10 days, but the CDC reports it can reemerge for several weeks.
An aerial view of the city of San Francisco skyline and the Golden Gate Bridge in California, U.S., October 28, 2021.
Notably, children between the ages of 5 and 9 years often become ill from this virus due to school outbreaks and close contact with other children. Adults who have not previously been infected with parvovirus remain susceptible and, with a weakened immune system, are at higher risk of complications, according to the CDC.
The CDC also notes that if a person contracts parvovirus B19 during pregnancy, the virus can spread to the baby. Although it’s not common, it could cause a miscarriage or problems with the unborn baby.
The CDC recommends that folks who are pregnant, have a weakened immune system or have an ongoing blood disorder should seek care from their local health care provider.
Where was parvovirus B19 detected?
Recent wastewater data collected by Wastewater SCAN, an online service based at Stanford University that monitors municipal systems for diseases, found that parvovirus detection has increased throughout the region.
The Tower Bridge, linking West Sacramento and Sacramento, sits next to Old Sacramento State Historic Park, on Friday, April 3, 2026, in Sacramento, California.
Notably, the virus was detected in San Francisco, Sacramento, Davis, Napa, Palo Alto, Redwood City, San Jose, Sunnyvale, Vallejo and the South County Region wastewater systems.
Wastewater SCAN noted that there was a moderate level of positive samples among these cities: San Francisco, Sacramento, Davis, Napa, Redwood and San Jose.
Credit: USA TODAY
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