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In April, the World Health Organization reported a record high of more than 6.5 million cases of people infected with dengue—a 55 percent increase in a single year. Most of those cases were outside of the United States. When an outbreak occurred in Florida two years ago, researchers took a closer look. Forrest Jones, an epidemiologist with the Centers for Disease Control and Prevention and a lead author of the report, spoke with Harvard Public Health.

Why study this topic?

The Florida Department of Health routinely looks for cases of dengue. The department also does dengue testing. It uses the data collected to find mosquito exposure locations and other suspected dengue cases. But we wanted to see who was getting infected, look for patterns, and genetically identify which of the four types of dengue virus infected individuals in Florida.

What did you find?

We identified infections reported primarily among travelers between Florida and Cuba. There were 601 travel-associated cases, an unusually large number. We looked at viral genetic code from 203 cases and found that the virus infecting all of them was from the same lineage. The same version of dengue caused 61 locally acquired infections as well, particularly in Miami-Dade County. With case monitoring and genetic testing on the virus, we identified a newly emerging dengue lineage.

What would you like to see happen based on your findings?

People should understand that in the last decade, dengue has been continually showing up where it hadn’t existed before. The virus found in the Florida cases had similar genetics to the dengue virus recently found circulating in the Americas, specifically in Puerto Rico, Brazil, and Arizona. We hope that people will take more precautions more seriously, like getting rid of standing water around the home and wearing an EPA-approved mosquito repellent.

-Leah Samuel

This post has been updated to correct its description of the genetic testing.
(Study in Emerging Infectious Diseases, February 2024)

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