Study ranks measles risk by US county, air travel route
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Researchers used county-level vaccination data and a model that distributed arriving travelers to counties near international airports to estimate the U.S. counties — and international travel routes — at highest risk for measles outbreaks.
“Decreasing vaccination rates, combined with an increase in measles outbreaks abroad and high volumes of international travel, places the USA at increased risk of measles introduction and local outbreaks,” Lauren Gardner, PhD, associate professor at Johns Hopkins Whiting School of Engineering, and colleagues wrote.
Gardner and colleagues expanded on a study they published last year that identified U.S. counties at the highest risk for measles outbreaks. For the current study, they used data on MMR vaccination rates from 40 states and a diffusion model to distribute inbound travelers to U.S. counties near international airports.
The model identified multiple regions in several states — California, New York, Washington, Texas and Florida — as having the highest risk for measles outbreaks. Among the 20 counties with the highest risk for outbreaks, 17 had at least one measles case in 2019 and accounted for more than 700 of the 1,276 total confirmed cases in the U.S. last year, the researchers reported.
WHO recently warned that disruptions from COVID-19 could potentially cause 80 million children worldwide to miss routine vaccinations. Findings from MMWR last year showed a 167% global increase in measles cases between 2016 and 2018, driven by gaps in vaccination coverage.
“It is important that public health authorities educate the public on the importance of routine vaccinations in the era of COVID-19,” Aaron E. Glatt, MD, chairman of the department of medicine and chief of infectious diseases at Mount Sinai South Nassau in Oceanside, New York, told Healio. “They need to stress and remind people when it is safe to go back for these vaccinations.”
According to the model, the five U.S. counties at highest risk for measles outbreaks are Los Angeles; King County, Washington (which encompasses Seattle); Honolulu, Miami and Orange County, California. It identified Israel, New Zealand, Ukraine, Samoa and the Philippines as the countries with the highest measles importation risk to the U.S. The air travel routes most likely to introduce measles to the U.S. all end in Los Angeles and originate from the Philippines, Samoa, New Zealand and Ukraine, according to the model.
The researchers noted that the study’s major limitations included the risk model’s inability to incorporate the risk for domestic spread and their use of only WHO-confirmed measles cases, which may underestimate risk in counties with limit case confirmation capacity.
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