Stomach Virus Surges Across California

California is seeing a spring rise in rotavirus, a stomach virus that hits babies and young children hardest and spreads fast in homes and child care settings. (cdc.gov) Rotavirus causes vomiting, watery diarrhea, fever and stomach pain, and symptoms usually last three to eight days. The most severe illness is concentrated in unvaccinated children ages 3 months to 3 years old, though older adults, caregivers and people with weakened immune systems can also get sick. (cdc.gov) Wastewater monitoring has picked up the virus in multiple California communities this month, with health agencies using sewage data to track whether circulation is rising or falling in a sewershed. California says those measurements cannot show the exact number of infections, but they do show community trends. (data.chhs.ca.gov) The virus spreads through stool particles that move from hands, surfaces, food or water into the mouth. The Centers for Disease Control and Prevention says rotavirus is stable in the environment, which helps it move quickly in places where many young children share bathrooms, toys and tables. (cdc.gov) That makes child care centers and similar group settings a recurring pressure point. California’s January 5, 2026 school and child care guidance lists vaccination, hygiene, staying home when sick and outbreak response as core steps for limiting spread of communicable diseases, including stomach viruses. (cdph.ca.gov) Unlike norovirus, rotavirus does have a vaccine — but it is only for infants, and the timing is tight. The Centers for Disease Control and Prevention recommends two or three oral doses, depending on brand, starting at 2 months, with the first dose before 15 weeks and all doses finished before 8 months. (cdc.gov) The vaccine changed the disease sharply after its rollout. The Centers for Disease Control and Prevention says it now prevents an estimated 40,000 to 50,000 hospitalizations a year in U.S. infants and young children and provides 85% to 98% protection against severe illness in the first year. (cdc.gov) California’s latest kindergarten immunization report does not track rotavirus because the vaccine series is completed in infancy, before school entry. The state did report 590,849 kindergartners in 2024-25, with 93.7% up to date on all required school-entry vaccines and county-by-county variation that health officials said remained wide. (cdph.ca.gov) Parents usually do not need a test to recognize the illness, but dehydration is the danger sign that changes the equation. The Centers for Disease Control and Prevention lists decreased urination, dry mouth, few or no tears, dizziness, unusual sleepiness and fussiness as warning symptoms that need medical attention. (cdc.gov) The practical advice is old-fashioned and specific: wash hands with soap and water, clean contaminated surfaces, keep sick children home and make sure infants get their doses on time. For a virus that can empty a day care room in a weekend, timing is most of the fight. (cdc.gov)