The Centers for Disease Control and Prevention is warning Americans to make sure they're fully protected against the measles before traveling internationally this summer.
The agency issued a health advisory Wednesday urging that people make certain they've had two doses of the measles-mumps-rubella, or MMR, vaccine at least two weeks before traveling to areas of the world with active measles outbreaks.
Those two doses provide 97% protection against the virus, according to the CDC. But an unvaccinated person is at extremely high risk of getting sick even with brief exposure.
A person "can get measles just by being in a room where a person with measles has been, even up to two hours after that person has left," according to the CDC’s website.
It's recommended that children get their first dose at 12 to 15 months, and the second dose around the time the child starts kindergarten, at age 4, 5 or 6. Teens and adults who have never had the shots should get two doses at least 28 days apart, according to the CDC.
Rising measles cases
There is new evidence that measles cases are ticking up again in the U.S. after falling during lockdown.
As of June 8, "the United States has seen an increase in measles cases during the first 5 months of 2023, with 16 reported cases compared with 3 in 2022 during the same period," the CDC wrote in the health alert.
Eighty-eight percent of those cases have been linked to international travel. Most patients had not been vaccinated.
Just this week, health officials in California confirmed two measles cases from one household in Fresno County. There was no word on how the two people became infected.
"These cases are reminders of the critical role of vaccinations in protecting the community," Dr. Rais Vohra, Fresno County's health officer, said in a statement to NBC News. "We urge all parents to please work with your pediatrician or contact the health department to help get your child up-to-date on vaccinations."
In 2019, two large outbreaks in New York sent cases soaring to levels not seen since 1992: 1,274 cases.
New outbreaks are increasingly reported in other areas of the world, too, especially India, Indonesia, parts of the Middle East and much of Africa, the CDC said.
In the United Kingdom, health officials say that since the beginning of the year, there have been 49 cases of measles, compared to 54 cases during all of last year.
A decline in MMR vaccinations
To best prevent measles outbreaks, 95% of a community should be vaccinated, according to the CDC. But vaccination rates declined during the pandemic, leading to pockets of vulnerability.
In November, the CDC and World Health Organization released a joint report that found 40 million children missed at least one dose of the measles vaccine in 2021 — a record high. The virus is an "imminent global threat," the groups said.
The CDC advisory recommended people talk with their doctor "several weeks before traveling abroad, regardless of your destination, to see if you or any dependents need MMR vaccine."
There is no specific antiviral treatment for measles.
Symptoms usually include a high fever, cough, runny nose, watery eyes, as well as a telltale rash that appears within the first week of illness, according to the CDC.
Babies and young children are most at risk for serious complications, including swelling of the brain and death. The virus can also lead to premature birth and low-birth-weight babies if a pregnant woman is infected.
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