World’s most contagious disease continues to spread in California as more clusters form

California is fighting a measles outbreak as two new cases were reported in Sacramento County on Monday — bringing the total to 34 across the state.

The latest cluster were unvaccinated children. Measles is of little harm to vaccinated people but can pose a risk to the unvaccinated, officials said.

“The continued identification of measles cases in our community is concerning and underscores how quickly this disease can spread,” Dr. Olivia Kasirye, Sacramento County Public Health Officer, said in a statement.

“Measles can cause serious illness but it’s important to remember these cases are preventable. Vaccination is the most important step people can take right now to protect themselves and others,” Kasirye added.

Health officials say the risk to public “remains low,” but they urged the public to “be hyper-aware and take steps to protect themselves and others.”

Measles is the world’s most contagious disease, but most children are given the measles, mumps, and rubella (MMR) vaccine — which provides long-lasting protection against all strains, the CDC said.

Symptoms appear within seven to 14 days of infection and include high fever, runny nose, rash and cough.

Cases have been reported in 33 states with 92% involving unvaccinated individuals or people with unclear vaccination histories. The U.S. has reported over 1,671 confirmed measles cases in 2026.

As for the two newly-infected children, they are in isolation and are recovering, Sacramento County health officials said.

LA County officials showed concern last month about the spread of measles.

“That’s ridiculously infectious,” Dr. Sharon Balter, director of acute communicable disease control with Los Angeles County public health, told Cal Matters.

“It balloons very quickly, and because measles spreads very fast we have to get on it right away. We can’t say we’ll wait until tomorrow.”

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