‘Very contagious’ parvovirus swirling throughout Northern California

This year, California has been facing an onslaught of lesser-known respiratory and gastrointestinal illnesses, and now, yet another highly transmissible virus is circulating throughout the region.   

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According to recent wastewater surveillance data, parvovirus B19, a “very contagious” respiratory illness that can cause a distinct rosy rash in children and lead to severe complications in pregnant people, is swirling throughout the South Bay and several Northern California cities. Parvovirus type 2 infects dogs, but parvovirus B19 is transmitted from human to human. 

The virus, which typically causes mild symptoms like muscle aches, fever and runny nose, has a moderate presence in Davis, Sacramento, San Jose, Napa, Palo Alto, Redwood City and the southeast neighborhoods of San Francisco, WastewaterSCAN data shows. Children between the ages of 5 and 15 who contract the virus are also more likely to develop a rosy, “slapped cheek” rash over a week after infection, also known as fifth disease. Overall, though, symptoms are usually mild, and sometimes people display no symptoms at all. People who are pregnant, however, face higher risks of severe complications like miscarriage.

Usually spread through coughing and sneezing, “Parvovirus B19 is highly transmissible in respiratory droplets, with 50% of susceptible people infected after household exposure and 20–50% of susceptible students and staff infected during school outbreaks,” an August 2024 notice from the Centers for Disease Control and Prevention says, adding that people who work with children face higher risks of contracting the illness. According to a 2026 study from child healthcare experts, the virus is seasonal and peaks in spring, late winter and early summer, and it usually resolves on its own. 

Though parvovirus isn’t routinely monitored in the U.S., the CDC reported higher rates of the virus in 2024 and 2025 compared with earlier years — and local health experts say it could be a byproduct of the pandemic.  

Dr. Monica Gandhi, an infectious disease specialist at UC San Francisco, previously told SFGATE that because COVID-19 was “quieter” this season, “other viruses like influenza and HMPV are getting their chance.” But it’s possible that California is paying a steep “immunity debt,” too. 

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Like its name suggests, immunity debt hypothesizes that the population ultimately became more vulnerable to other common diseases following COVID-19 restrictions.   

According to an April 2025 international study, though social distancing and lockdown measures were enforced to prevent the spread of COVID, it also prevented the spread of other common illnesses. Once these restrictions were relaxed, the authors noted a “resurgence” of these illnesses, as well as a rise in respiratory infections in the U.S. Though the hypothesis is unconfirmed, it is supported, the authors wrote. “I think that’s a real phenomenon,” Gandhi told SFGATE Tuesday, adding that health experts “have always wondered about children and their need to be exposed.” 

For now, she recommends that pregnant people in the South Bay take extra precautions around anyone who displays symptoms of respiratory illness. 

There is no vaccine or treatment available for parvovirus B19, but individuals can help prevent the spread by covering their faces when coughing and regularly washing their hands, especially after touching potentially contaminated surfaces. Health experts recommend that pregnant people wash their hands regularly and avoid close contact in settings like daycare centers and schools where parvovirus has been confirmed. The CDC advises people to stay home when sick with a respiratory illness.