Los Angeles County officials dealing with a measles outbreak say they expect that more people will be diagnosed with the illness in the coming weeks, while the nation stares down what will likely be its worst measles year in decades.

But where are these cases coming from? The U.S. declared measles eliminated in 2000, and the virus does not regularly circulate here.

Officials say that every person diagnosed with measles in the U.S. either contracts it abroad or from someone who got it abroad. In the past few years, American tourists have become more likely to encounter measles because of massive outbreaks in other countries, experts say.

The World Health Organization reported that measles cases worldwide increased 300% in the first three months of 2019 compared with the previous year. In countries such as the Philippines, Ukraine and India, tens of thousands of people come down with measles each year, according to the agency.


The problem is compounded when unvaccinated American travelers bring measles back to communities with low vaccination rates, where the disease can rapidly spread, experts say.

The nation’s biggest outbreak this year began when travelers to Israel contracted measles, which then gained a foothold in an unvaccinated segment of New York’s ultra-Orthodox Jewish community.

“This is a worldwide problem, this isn’t just a U.S. problem,” said California state Sen. Richard Pan (D-Sacramento), a pediatrician who advocates for stricter vaccination laws . “It also shows that we are constantly being bombarded by these diseases — they’re looking for a crack, or a way to get in.”

Hundreds still quarantined

L.A. County officials declared a measles outbreak last week, which led to more than 1,000 people being told to stay home because they may have been exposed to the virus.

As of Monday afternoon, 27 UCLA students and 221 Cal State L.A. students and staff remained under quarantine due to the outbreak, according to university officials. If they don’t have measles symptoms, the UCLA students will be released Tuesday and the Cal State L.A. students Thursday, county officials say.


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The problems began when an L.A. County resident visited Vietnam earlier this year and contracted measles, said L.A. County health officer Dr. Muntu Davis. That person then spread measles to three other people in L.A. County.

A fifth case of measles popped up in L.A. County after a resident took a trip to Thailand, he said.

“There’s a high number of cases in many other countries and people are traveling more,” Davis said in a call with reporters. “We expect that we may see more cases of measles inside Los Angeles County.”


Of the five people sick with measles in L.A. County, one is a Cal State L.A. student and one is a UCLA student, but Davis would not specify further for privacy reasons.

Officials advised that anyone leaving the country has the two recommended doses of the measles vaccine, which are together estimated to be 97% effective. None of the five people had both doses, they said.

“If you’re traveling internationally, your risk is much, much higher right now,” said L.A. County acute communicable disease control director Dr. Sharon Balter.

In California, 14 of 38 people with measles this year became sick while visiting other countries, including India, Thailand, the Philippines, Vietnam, Cambodia and the Ukraine, according to state health officials. Four of those people infected 22 other people in the state, most of whom weren’t vaccinated, they said.


Measles is one of the most contagious diseases in the world, so just one case can lead to hundreds more, experts say. The lower the vaccination rates in the neighborhood where measles appears, the more people who will end up catching it, said Dr. Mark Roberts, chair of health policy and management at the University of Pittsburgh Graduate School of Public Health.

“What matters is not the case that starts it, what matters is how many people that one case infects,” Roberts said.

L.A. County officials said that one measles case could spread to 600 people within a few weeks if steps were not taken to quarantine people who were exposed and may develop measles. As of Monday, officials had not reported that any quarantined people had shown measles symptoms.

California tends to have higher-than-average vaccination rates, which may have spared the state from the big outbreaks elsewhere in the country. California has one of the strictest vaccination laws in the country, passed in the wake of a measles outbreak at Disneyland in 2014.


“We do see things popping up,” said Pan, who authored the vaccine law. “So far, it seems like none of these individual instances have really taken hold in a way where they have blossomed into an outbreak of 50 or 100 people.”

Links to Philippines

California’s biggest outbreak is in Butte County, about 90 miles north of Sacramento. That cluster, which now includes 16 people, began when a man visited the Philippines, according to state health officials. (The Disneyland outbreak from 2014 is also thought to be linked to the Philippines.)

The Philippines is in the midst of a massive measles outbreak, fueled by fears of the side effects of vaccines, according to the World Health Organization. For the first time, the agency in 2019 named vaccine hesitancy one of the world’s greatest health threats.

In the first three months of this year, 355 people died of measles in the Philippines and another 25,000 were diagnosed with the illness, according to the agency.


By contrast, in the U.S. — a country three times bigger than the Philippines — no one has died of measles this year and 704 people have been diagnosed with the illness so far.

Still, it’s imperative that as many people as possible in the United States become vaccinated to protect those who cannot be immunized or for whom immunization does not work, said Johns Hopkins infectious disease professor Clare Rock.

Not long ago, the nation’s vaccination rates were high enough that measles could not spread here at all, she said. But now clusters of unvaccinated people can allow the disease to take hold, she said.

“It seems like now we’re in a situation where we don’t have the same levels of vaccination that we’ve had in the past, and that means a lot of our population is vulnerable,” she said.


soumya.karlamangla@latimes.com

Twitter: @skarlamangla