TAMPA — Hillsborough County is one of the nation's most at-risk areas for a measles outbreak, according to a study published this week.
It was one of four Florida counties ranked in the top 25 most vulnerable areas in the country, says the study, produced by researchers at the University of Texas at Austin and Johns Hopkins University.
Miami-Dade is the most susceptible county in the Sunshine State, ranking third in the nation. Broward County ranked seventh, Orange County was 14th and Hillsborough was 17th.
The rankings are based on low-vaccination rates compounded by a high volume of international travel. Based on those factors, researchers identified Cook County, Ill., as most in danger of a measles outbreak in 2019. The findings were published Thursday in the online medical journal The Lancet.
More than 700 measles cases have been confirmed in the first four months of this year, according to the study. That's the highest number reported since measles was thought to be eradicated in the U.S. in 2000.
Hillsborough's risk for an outbreak has been on the rise since 2016, the study says.
For the current school year, 1,447 students in the county were granted religious exemption status for immunizations, according to the Florida Department of Health. That's 5.8 percent of the student population.
Their numbers are up from 2014, when 734 students — or 5.59 percent of those enrolled in the county — received religious exemptions.
The researchers observed that measles cases don't respect county lines and recommended that local officials be alert for outbreaks in adjacent counties.
In 2018, officials in neighboring Pinellas County reported seven measles cases after there had been no such cases for 20 years. None of the patients had been vaccinated, they said.
Measles is easily transmitted, highly contagious and can be spread through the air. In the study, each county's at-risk ranking was derived from multiple factors, including international air travel, county population, the incidence rate of measles outbreaks and the number of non-medical vaccine exemptions reported in that county.
The epidemic will worsen, researchers warn, as more and more parents choose not to vaccinate their children.
"The vaccine avoidance problem is not limited to measles," the study's lead author, University of Texas at Austin professor Sahotra Sarkar, said in a statement. "Pertussis — whooping cough — is another disease making a comeback because of dropping vaccination rates, and we predict serious outbreaks in the U.S. in the near future."
Sarkar encouraged policymakers to focus on regions with lots of airline passengers traveling from affected countries, especially if there are even small local pockets of unvaccinated people already living in that county. The researchers warned the most at-risk areas that have yet to report a case are those with international airports, such as Miami, Orlando and Tampa.
They said their risk analysis correctly predicted reported measles outbreaks in Washington, Oregon and New York. Two-thirds of the counties that have reported measles cases to the Centers for Disease Control and Prevention were either included on the researchers' list of 25 high-risk counties or are adjacent to a county listed.
Travel to and from China, India, Japan, Mexico, the Philippines, Thailand and Ukraine appears to pose the greatest measles risk, according to the study. The U.S. has already seen measles cases imported from the Philippines, Thailand and Ukraine.
Staff writers Justine Griffin and Kirby Wilson contributed to this report. Contact Caitlin Johnston at firstname.lastname@example.org or (727) 893-8779. Follow @cljohnst.