Correction: An earlier version of this article incorrectly described when a Washington state law on vaccines went into effect, which occurred on July 28.
As students head back to school, physicians and public health officials are pleading for parents to immunize their children.
This year has seen the most reported cases of measles in the USA in more than 25 years. Among those at the highest risk of serious complications or death because of the viral infection are unvaccinated children.
"Traditionally, when we've had measles epidemics in America in the pre-vaccine era, they would peak in the late winter and early spring," said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston. "This seems to be following that similar pattern."
The very contagious disease was once declared eliminated in the USA, but it has made a comeback in recent years, in part because of the spread of misinformation about vaccines. Last week, the Centers for Disease Control and Prevention reported 10 new measles cases, bringing this year's total to 1,182.
The measles outbreak isn't limited to the USA. According to a report Monday from the World Health Organization, this year's worldwide total of measles cases is at a 13-year-high and about three times the number of cases reported at the same time last year.
More severe measles outbreaks have occurred in Angola, Cameroon, Chad, Kazakhstan, Nigeria, the Philippines, South Sudan, Sudan and Thailand. European countries reported nearly 90,000 cases for the first half of 2019 – exceeding the 84,462 total cases observed all last year.
In the USA, worldwide travel has been a factor in several cases.
Last week, the County of San Diego Health and Human Services Agency confirmed measles in an 11-month-old child who contracted the illness in the Philippines. According to a report May 27 from WHO and UNICEF, the island nation had seen 34,950 measles cases and 477 deaths this year.
The baby has made a full recovery and no further cases have been reported, said Eric McDonald, medical director of epidemiology and immunization for the County of San Diego. Nonetheless, McDonald said the county would remain vigilant in coming months.
"There are a lot of measles cases throughout the world right now," McDonald said. "When we have a lot of people traveling internationally from San Diego, we're always at an increased alert."
In another recent case, a flight attendant working for the Israeli airline El Al died after contracting measles on a flight from New York City to Tel Aviv, Israel. According to reports from Israeli media, it's the country's third measles-caused death since last November. Before that, Israel hadn't experienced a single fatality from the viral infection in the past 15 years.
Though the USA has seen measles outbreaks before, the global aspect of the illness's resurgence presents an unfamiliar threat, Hotez said. Making the health crisis worse are parents who don't want their children to get vaccinated. A report in 2017 from the Pew Research Center found that 17% of U.S. adults said parents should have the right to decide whether their child should be vaccinated, "even if that may create health risks for others."
Hotez was part of a team of researchers that conducted an academic study last year that analyzed 14 U.S. metropolitan areas where more than 400 kindergartners had been excused from vaccines because they received "philosophical-belief nonmedical exemptions." Fifteen states allow students philosophical exemptions for some vaccines.
"What we don't know is what happens as kids are going back to school," Hotez said. "You have a new issue, which is that measles is now widespread in Europe, and it's continuously being reintroduced into the United States because of air travel. Because we have large numbers of unvaccinated kids now in at least 15 urban counties in the U.S., we may see an uptick again as we move into the fall."
On July 28, a new state law prohibiting residents from receiving the philosophical exemption for the MMR vaccine against measles, mumps and rubella took effect in Washington state. The decision was in part a response to one of this year's biggest national outbreaks.
Washington Gov. Jay Inslee declared a state of emergency Jan. 25after the statewide measles case count climbed to 26 in the first few weeks of 2019. All but one of the cases were reported from Clark County, Washington – a county of about 480,000 people in the southwestern corner of the state.
The county immediately took action, identifying susceptible, unvaccinated populations and quarantining them from others. According to Alan Melnick, the county's public health director and health officer, the county had more than 800 people placed on active surveillance.
Since May, Clark County has reported zero measles cases.
In a county report that followed the outbreak, officials found that of the 71 overall cases reported by April 29, 61 of them included unvaccinated patients. In seven other cases, vaccination statuses were reported as "unverified." The other three patients had received one dose of the MMR vaccine.
Though Melnick said immunization rates for children and adults skyrocketed in the weeks after the outbreak, he is worried another outbreak is imminent for Clark County.
"Measles exists in the world. It exists in the United States. It's just a car ride, bus ride, plane ride or train ride away," Melnick said. "And we continue to have populations that are unvaccinated."
For many in the U.S. medical community, watching the outbreak unfold has been a disappointing experience.
"So much of medicine is centered around trying to find treatment and trying to find ways to prevent illness, so it's extremely disappointing to see people contract a disease that we know is preventable," said Lisa Maragakis, senior director of infection prevention for the Johns Hopkins Health System in Maryland. "We have a way to prevent it."
This article originally appeared on USA TODAY: Measles outbreak could worsen as school resumes, experts say