Where the Next Big Measles Outbreak Could Happen
By Katherine Rosenberg-Douglas
Researchers who in 2015 correctly predicted where the Zika outbreak would strike in the U.S. say they think the country's next big measles outbreak is most likely to happen in Cook County.
A research project spearheaded by Sahotra Sarkar, a University of Chicago-educated professor at the University of Texas at Austin, revealed the 25 counties most at-risk for a widespread measles outbreak, like those seen in Washington, Oregon and New York. Sarkar and his former student, Lauren Gardner of Johns Hopkins University, determined Cook County was the most at-risk for an outbreak. That's based largely on the number of airplane flights to Chicago from global destinations where parents increasingly don't have their children vaccinated, he said.
"Cook County turns out to be as important as it is, mainly because of the presence of O'Hare Airport," Sarkar said.
The study was published Thursday in The Lancet Infectious Diseases. The research took about six months to complete, using risk assessment models similar to one Sarkar and Gardner used when they determined Zika, a mosquito-carried virus that can cause serious birth defects, would first affect Texas and Florida when it emerged as a global threat to pregnant women.
Rachel Rubin, a senior medical officer with the Cook County Health Department, wasn't surprised by the study's findings. The seven measles cases reported in Illinois this year likely stemmed from one person who was infected overseas and traveled back to Illinois, she said.
"As we know O'Hare is a huge transfer point for travel within the United States, not to mention all of the international flights," she said. "I'm not surprised that their modeling would've predicted that Cook County and the city of Chicago would be such a hot spot."
Rounding out the top 10 counties identified in the study as most at-risk for a measles outbreak are: Los Angeles; Miami-Dade; Queens, N.Y.; King, Wash.; Maricopa, Ariz.; Broward, Fla.; Clark, Nev.; Harris, Texas; and Honolulu.
Since the 2015 work on Zika, Sarkar learned that a widely discredited former physician who claimed the vaccine for measles, mumps and rubella can cause autism has relocated to Austin and gained a following. Sarkar did the measles study to warn people what could happen if they choose "conspiracy theories" over science.
"It occurred to me that perhaps besides the vaccine resistance from people who bought into this false notion that the MMR vaccine has a link to autism ... the other crucial factor would be the volume of travel from countries outside the U.S. where there have been epidemics," including in European countries and the Philippines, Sarkar said.
Sarkar points to what happened in Brooklyn in October, after unvaccinated children visited Israel during a monthslong measles outbreak. They returned to their community, made up mainly of ultra-Orthodox Jews, many of whom have chosen not to vaccinate their children with MMR because they believe the vaccine is not kosher. What followed was one of the nation's largest outbreaks, prompting New York's Rockland County to declare a state of emergency, banning unvaccinated children from visiting public places.
The Illinois Department of Health recently announced it is working with the Illinois State Board of Education to conduct an in-depth analysis focusing on schools at risk for outbreaks. It also is taking steps to increase vaccination rates across the state.
Despite that, the state health department does not make public statistics on "vaccine avoidance," Sarkar said. It isn't clear whether there are enclaves of families who refuse to vaccinate based on religious beliefs or because they distrust vaccine safety.
"Estimated vaccination rates are low even though vaccination is mandatory and there are no nonmedical, nonreligious exemptions (allowed) in Illinois," Sarkar said.
"If there are pockets of resistance in Cook County like there were in Brooklyn with the ultra-Orthodox Jewish community, then there's a very serious worry."
Rubin doesn't know of any particular enclaves where people avoid vaccines because of religious edicts. But she does sometimes encounter objections to vaccines. When that happens, she tries to be diplomatic in explaining their safety and efficacy.
"It's a bad choice to refuse vaccination just because you feel that you don't want it, based on your own philosophical reasons," she said.
Rubin and Dr. Tina Tan, an infectious disease specialist at Lurie Children's Hospital, said having a high vaccination rate is most important for people who are allergic to vaccines or suffer from an ailment that suppresses the immune system, making it impossible for those children to receive a vaccine. For measles, more than 95 percent of the population needs to be vaccinated to guard against measles ourbreaks.
Sarkar said he now recommends infants get their first MMR vaccination at 6 months because of how many children remain unvaccinated in his area. The dose at 6 months may not be as effective as a dose given at 12 months, but when there's an outbreak, something is better than nothing, Sarkar said.
Countries that are particularly dangerous, Sarkar said, include India, China, Mexico, Japan, Thailand, the Philippines and a number of European countries. Those include Ukraine, the United Kingdom, France and Italy.
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