Public health officials urge vaccinations and symptom monitoring as measles cases climb across Southern California and the nation
A child in Riverside County tested positive for measles, marking the county’s first confirmed case of the year and raising concerns among public health officials about declining vaccination rates and renewed vulnerability to preventable diseases.
Measles is one of the most contagious human diseases, with a single infected person capable of transmitting the virus to 12 to 18 susceptible people in an unprotected population, and up to 90 percent of susceptible close contacts becoming infected.
The virus incubates for about 7 to 21 days after exposure, typically around 11 to 14 days before symptoms such as high fever, cough, runny nose, and rash appear. Infected persons can shed the virus from four days before to four days after rash onset.
Investigators found no recent international or out-of-state travel, pointing to possible community transmission similar to recent outbreaks among unvaccinated groups. Public health teams continue tracing contacts, noting the measles virus can remain airborne in enclosed spaces for up to two hours. Officials urge exposed individuals to monitor symptoms and contact health providers immediately.
Measles spreads easily through respiratory droplets released when an infected person coughs, sneezes, or speaks. The virus can remain in the air for up to two hours after exposure. Symptoms typically include fever, cough, runny nose, red eyes, and a rash that starts on the face and spreads across the body. Health experts say measles can lead to serious complications, especially in young children and people with weakened immune systems.
The Riverside County case comes as measles cases increase across Southern California and the nation. Public health experts report 733 confirmed U.S. measles cases so far in 2026, compared with 285 cases in 2024. Experts link the resurgence to declining vaccination coverage, with national MMR rates falling below the 95 percent threshold. Health officials warn that lower immunization levels allow measles to spread faster and produce larger outbreaks.
A 2025 report showed measles, mumps, and rubella (MMR) vaccination rates among California kindergartners dipped slightly from 96.5 percent to 96.2 percent in the 2023-24 school year, though they remained above the 95 percent threshold for community immunity.
Doctors emphasize that the measles, mumps, and rubella vaccine provides long-term protection against measles infection. Health officials recommend two doses, with the first around age one and the second before school entry. Studies show two doses prevent about 97 percent of measles infections in vaccinated individuals.
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Riverside County health officials urge parents to review their children’s immunization records and contact providers if any vaccinations are incomplete. Clinics across the county continue offering routine and catch-up vaccinations for children and adolescents. Officials advise anyone with measles symptoms to call a medical provider before in-person care to limit exposure.
Public health leaders say the case shows how quickly vaccine-preventable diseases can return when coverage declines. Officials warn that even small drops in immunization rates weaken community protection. Health authorities stress that high vaccination rates remain the most effective defense against measles outbreaks.
