Public health officials monitoring the measles outbreak in Shasta County are holding their collective breath.
That’s because while no additional cases of the disease have been reported since Feb. 9, local investigators found about 160 contacts of the county’s original case reported on Jan. 30, said Dr. Eric Sergienko, chief of the division of communicable disease control at the California Department of Public Health (CDPH).
Those potential exposures need to get through the 21-day infectious period to make sure no more cases develop, Sergienko told NSPR on Feb. 12.
“We’re in that watchful, waiting [period] and being hopeful that there aren’t any additional secondary cases from that index case in Shasta,” he said.
Shasta County’s eight cases represent about half of California’s 17 confirmed cases this year. Across the nation, 2026 is shaping up to be one of the worst years for measles cases since the disease was declared eliminated in the U.S. in 2000.
California’s measles risk remains low, however, Sergienko said. The state enjoys an overall immunization level above 95%, the mark needed to prevent community spread, he said.
But there are pockets in the state where local vaccination rates trail that critical percentage, giving the measles virus a better chance at breaking out and infecting more people.
Newly released state data for the 2024-2025 school year shows that 94.4% of kindergartners in Shasta County had received the full two-dose series of the measles vaccine. Two other North State counties also fell short of the community protection threshold. In Glenn County, the kindergarten vaccination rate was 84.5%, and in Trinity County it was 90.4%.
Sergienko said the challenge for infectious disease experts is convincing people to take vaccines for preventable diseases like measles even after the illnesses fade from public life.
“As vaccines are so effective, so good at preventing disease, people say, ‘I don't need this anymore. ‘It's no longer a problem,’” he said. “But then when people stop taking the vaccine, then you're increasing risk.”
Outbreaks in South Carolina, Arizona and Utah this year have added to the likelihood that the U.S. will lose its measles elimination status this spring, NPR reported.
What are measles symptoms?
Measles is highly contagious and spreads primarily when an infected person coughs, sneezes, talks or breathes, according to the CDPH. It can last in the air for up to two hours.
Symptoms include:
- Cough
- High fever
- Runny nose
- Pink eye
- Rash
People who contract the disease are typically contagious from four days before their rash starts to four days afterward, according to the Shasta County Health and Human Services Agency.
The measles vaccine is recommended to prevent serious illness in young kids and pregnant people, according to the CDPH. The disease can cause pneumonia, brain swelling, hospitalization and even death.
If you’re vaccinated, how protected are you?
Yes, the measles vaccine is the best way to protect against the disease, Dr. James Mu, Shasta County’s health officer, previously told NSPR.
Two doses of the vaccine over a lifetime — typically given in childhood — are 97% effective at preventing measles, according to the Centers for Disease Control and Prevention.
People can check their vaccination records on California’s Vaccine Record Site.
How many people need to be vaccinated against measles?
Community protection against measles requires 95% of a population to be immunized against the disease, according to the World Health Organization (WHO).
“The remaining 5% will be protected by the fact that measles will not spread among those who are vaccinated,” the WHO website states.
The vast majority of measles cases – about 90% – happen in unvaccinated people, the CDPH reported.
