LOS ANGELES — Public health officials in Los Angeles have declared a measles outbreak in the county, making it the latest metropolitan area to be hit by the illness and part of a national surge in cases rapidly approaching record numbers.
Five cases of measles are being investigated by the Los Angeles County Department of Public Health. Though vaccination rates are typically high in California, a single case can easily spread — not only to those who are not vaccinated, but also to infants who cannot yet receive immunization and to elderly patients with suppressed immune systems.
The public health department said the transmissions are the first confirmed in the county this year. The department believes additional exposures may have occurred in April at Los Angeles International Airport, at several buildings on the University of California Los Angeles campus, at a library at the California State University in Los Angeles, and at several restaurants near Glendale.
Officials did not indicate the ages of those infected but said the majority of individuals were unvaccinated.
Nationally, there have been 626 confirmed cases of measles across 22 states so far this year, already the second-highest number since 2000. And the numbers are growing rapidly. In the last week, 71 new cases were confirmed. A Centers for Disease Control and Prevention spokesman said Tuesday that the agency is expecting the number of cases in 2019 to exceed 2014, when there were 667 cases.
It does not have to be this way, say physicians and public health officials: The United States declared measles “eliminated” in 2000, meaning that it was no longer endemic because of the country’s strong vaccination system.
But cases still occur among people who are not vaccinated, and measles can be carried into the United States from other countries.
Convincing individuals and communities who oppose vaccination to get immunized has proved difficult for some political leaders. In New York City earlier this month, amid a growing crisis, Mayor Bill de Blasio declared a public health emergency, requiring residents of some Brooklyn neighborhoods to receive the measles vaccine.
In California, there have been 23 confirmed cases of measles so far this year, according to the most recent numbers available through the state department of public health. That number is expected to grow, as well.
A single measles case can quickly spiral into an outbreak, especially because people with measles might not know they have the illness for several weeks before they start exhibiting symptoms.
In an outbreak in Butte County in Northern California this year, a single individual transmitted measles to eight other people across several counties.
People who do contract measles often eventually seek medical care at hospitals, where they can potentially transmit the illness to other patients, especially those with compromised immune systems. Infants typically do not receive measles vaccinations until they are about 1 year old and therefore are highly vulnerable.
“The best protection for infants is to have all of the family members vaccinated,” said Dr. Karen Smith, the director of the California Department of Public Health. “One of the things we’re doing very, very aggressively is working with hospitals particularly to make sure they are asking about travel when someone comes in with symptoms that could be measles.”
Though it is rare, people who have been vaccinated have been known to develop measles, typically because their immune system is compromised in some way. Elderly people are often at high risk, as are patients who take medication that affects the immune system, like those being treated for arthritis.
In 2015, a single infected visitor to Disneyland in Anaheim led to a 147-case outbreak across California and several other states.
“Twenty percent of the adults who got measles in that outbreak were hospitalized. Measles is not a benign condition,” Dr. Smith said. “In adults, it can cause an inflammation of the brain just as it can in children, and that can be severe, and it can leave adults with a long-term intellectual disability.”
But medical recommendations regarding vaccination have been rejected by some parents who are skeptical of the accepted science. Some believe immunization may even be harmful, which goes against medical consensus.
The 2015 outbreak in California motivated Leah Russin, the executive director of Vaccinate California, who lives in Palo Alto, to become a pro-vaccination activist. As a new mother during that time, she learned that some parents were opting out of vaccination, which made her deeply anxious about the health of her baby.
Ms. Russin said she strongly believes people have the right to make their own parenting decisions. But she said vaccination is about protecting the most vulnerable, not about parenting trends.
“If you want to nurse your child until he’s 15, fine! That’s not going to impact anybody else. If you want to co-sleep, talk to your doctor about how to do it safely. That’s your choice,” she said. “But vaccinating goes beyond that. Vaccinating affects your community.”