Pockets of unvaccinated communities are driving measles outbreaks in
California
[March 03, 2026]
By KRISTEN HWANG/CalMatters
When a possible measles case is identified in California, a phone rings
at the local health department and the clock starts ticking.
Laboratory workers need to process samples as soon as possible to
confirm the case. And a public health nurse must call the patient to
find out where they’ve been and who they’ve been in contact with
recently.
If test results are positive, the communicable disease team has 72 hours
or less to identify anyone who has been exposed and may be at high risk
of infection or serious illness. Those people must quarantine or take a
dose of a post-exposure prophylaxis to prevent spread. For the next 21
days nurses will monitor the group for symptoms.
Measles is the most contagious vaccine-preventable viral infection in
the world, and California is fighting multiple outbreaks. In a room
where one person is infected, nine out of 10 unvaccinated people will
also contract the disease. The viral particles also linger in the air
long after the contagious person leaves, risking exposure to those who
enter the room up to two hours later.
“That’s ridiculously infectious,” said Dr. Sharon Balter, director of
acute communicable disease control with Los Angeles County public
health. “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.”
California has a high enough vaccination rate — about 95% of
kindergarteners — to provide herd immunity against measles, but
throughout the state pockets of unvaccinated communities drive
outbreaks, experts say.
Shasta and Riverside counties are working to contain localized
outbreaks. These are the first measles outbreaks in the state since 2020
and are happening at a time when health departments have less money and
fewer staff than in recent years. In total, seven counties have reported
a total of 21 measles cases this year, according to the California
Department of Public Health.
Throughout the country, 26 states have reported measles cases since the
start of the year, including a massive outbreak in South Carolina where
officials identified nearly 1,000 cases, mostly among unvaccinated
children. It is the largest outbreak since the Centers for Disease
Control and Prevention declared measles eradicated more than 25 years
ago.
“The United States is experiencing the highest numbers of measles cases,
outbreaks, hospitalizations and deaths in more than 30 years, driven by
populations with low vaccination rates,” said California Public Health
Officer Dr. Erica Pan in a statement earlier this month. “We all need to
work together to share the medical evidence, benefits, and safety of
vaccines to provide families the information they need to protect
children and our communities.”
Containment comes with high costs
Investigating any communicable disease is time-intensive and expensive.
The first three measles cases reported in L.A. County this year cost an
estimated $231,000, according to a health department analysis.
Why does it cost so much? Because a disease investigation often requires
a legion of public health nurses, physicians, epidemiologists and
laboratory scientists to follow-up with hundreds of contacts, Balter
said.
That includes sometimes visiting homes or exposure sites. For example, a
recent exposure at a daycare required nurses to wring urine out of used
diapers to test babies for measles. County health workers monitored 246
people who had been exposed to those first three measles cases — and the
work is ongoing.
On Feb. 19, the county reported its fourth measles case. All of them
were related to international travel. Other cases in California also
have primarily been related to travel either internationally or to
states where there are outbreaks. An unvaccinated child in Napa County
contracted measles in January after traveling to South Carolina.
Riverside County health officials reported one measles case where the
child had not traveled recently, and Shasta County health officials
suspect their first case could be related to travel in Southern
California but are waiting for DNA testing for confirmation.
Orange County reported two travel-related cases this year.
Health departments have fewer resources, more cases
Local health departments rely heavily on federal funding to prevent the
spread of infectious diseases, but last year, the Trump administration
slashed nearly $1 billion of public health funding from California. This
year it attempted to claw back another $600 million from California and
three other Democratic states.
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Pending lawsuits froze the cuts, but local health departments are
treating the money as a lost cause because they cannot bear the
financial risk if a judge eventually rules in favor of the Trump
administration.
Consequently, health departments closed clinics, terminated programs and
laid off dozens of workers.
“What we can do with less is less unfortunately,” Balter said. L.A.
county is facing a $50 million shortfall due to federal, state and local
cuts and recently closed seven public health clinics.
Health departments are also confronting decreased public confidence: The
high-profile questioning of vaccine safety and effectiveness by U.S.
Secretary of Health and Human Services Robert F. Kennedy Jr. has
complicated public health’s struggle to contain the spread of
preventable infections.
California Democratic leaders are aggressively fighting Kennedy’s
direction. They sued to block the administration’s new vaccine
guidelines, which stripped universal recommendation from seven childhood
vaccines. They blame Kennedy and the Trump administration for
“dismantling” the Centers for Disease Control and Prevention and stoking
fears over debunked claims that vaccines cause autism.
The state also released its own vaccine guidelines and formed an
alliance among four western states to share public health information
and recommendations.
“Everything including the outbreaks, the financial cuts, the questions
from the federal government that are arising are making our work very
difficult,” said Dr. Regina Chinsio-Kwong, Orange County public health
officer.
Twelve years ago, Orange County was the site of California’s largest
measles outbreak in decades. An exposure at Disneyland from an unknown
source infected 131 Californians and spread to six states, Canada and
Mexico.
The outbreak, which lasted four months, spurred state lawmakers to pass
some of the strictest childhood vaccine requirements in the country.
But even a single measles case requires “vast amounts of infrastructure”
to contain, Chinsio-Kwong said. On average, the department identifies
and monitors 100 exposed people per case. Since the start of last year,
Orange County has lost $22 million in federal cuts to public health. The
department is trying to protect their communicable disease surveillance
work, but it gets harder with every cut.
“We’re trying to prioritize our communicable disease control division,”
health officer Chinsio-Kwong said. “There are a lot of different federal
cuts, but we’re putting that as front and center: That has to be saved
no matter what.”
Measles spread in unvaccinated groups
Six hundred miles north, Shasta County is grappling with its first
measles cases since 2019 and the state’s largest outbreak of the year.
In late January, a sick child visited a health clinic in Redding with
measles symptoms that laboratory testing later confirmed. Health
officials interviewed 278 people and identified six locations where
others were exposed: a restaurant, a church basketball game, a gym, a
park, Costco and the clinic.
They also identified seven other cases among family members or neighbors
who were in close contact with the child.
It can take 21 days from the time of exposure for measles symptoms to
develop. On Feb. 19, just before the end of that period, health
officials confirmed a ninth case.
That person didn’t recognize the symptoms and visited several places
while contagious, including a school, a church service, a basketball
game and a clinic, said Daniel Walker, a Shasta County supervising
epidemiologist. Now, the contract tracing process has started over. The
communicable disease team expects to interview even more people this
time.
All cases have been among children who were unvaccinated or did not know
their vaccination status.
“It’s a great time to get immunized, because you can’t know when you’re
next going to be exposed…especially because we’re in an outbreak
situation,” Walker said.
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