Florida on alert as state declares emergency over ‘breakbone fever’ dengue outbreak

Florida has declared a local state of emergency over a dengue fever outbreak after health officials reported a sharp rise in locally acquired cases, including one death.

The state has recorded nearly 200 locally acquired dengue infections this year across several counties, including Pinellas County, home to St. Petersburg, and Hillsborough County, which includes Tampa. The total is already among the highest recorded in Florida in recent years.

Florida reported 199 locally acquired cases in 2023, while just 62 cases were reported last year.

Why are Florida officials concerned?

Dengue, sometimes called “breakbone fever” because of the severe muscle and joint pain it can cause, is usually associated with international travel in the United States.

Many dengue infections reported in the country occur among people who have recently traveled to regions where the virus is common, including the Caribbean, Central and South America, Southeast Asia and the Pacific Islands.

The concern in Florida is the number of infections acquired locally, meaning people were infected without recently traveling to a dengue-endemic region.

The development is particularly notable because locally acquired dengue outbreaks in the continental United States remain relatively uncommon.

The last major outbreak of dengue acquired outside the Texas-Mexico border region occurred in Key West, Florida, in 2009 and 2010. Before that, locally acquired cases outside the Texas-Mexico border area had not been reported since 1945.

How dengue spreads

Dengue is caused by a virus transmitted primarily by infected Aedes mosquitoes. These mosquitoes thrive in warm conditions, and experts have warned that changing climate patterns could expand the areas where they are able to survive and reproduce.

Florida's current outbreak is centered north of Tampa, where mosquito-control workers have been spraying to reduce mosquito populations and inspecting properties for standing water.

Paolo Pecora, a senior environmental scientist with Hillsborough County Mosquito Management Services, said workers have been checking places such as discarded tires where mosquitoes can breed.

Recent mosquito sampling has not detected the dengue virus, Pecora said, suggesting the likelihood of additional infections may be declining.

What happens when someone gets dengue?

Dengue infections do not always cause symptoms. That means the number of confirmed cases during an outbreak may not reflect the true number of infections.

When symptoms do occur, they can include high fever, headache and flu-like illness. In more serious cases, dengue can cause severe bleeding, shock and potentially death.

The World Health Organization has reported more than 2.2 million dengue infections globally so far this year, with nearly 1,200 deaths.

In the United States, the Centers for Disease Control and Prevention has reported nearly 1,500 locally acquired dengue cases, with most occurring in Puerto Rico.

Could dengue become more common in Florida?

Dengue outbreaks in the continental U.S. can begin when an infected traveler returns from an area where the virus is circulating. If that person is bitten by a mosquito capable of transmitting dengue, the mosquito can subsequently infect other people.

Michael von Fricken, an associate professor of environmental and global health at the University of Florida, said Florida's recurring populations of dengue-carrying mosquitoes mean the risk is unlikely to disappear entirely.

“I do think it’s going to be somewhat the new normal,” von Fricken said.

The Centers for Disease Control and Prevention has previously warned that locally acquired cases highlight the need for stronger surveillance, mosquito control and public-health preparedness in areas where dengue-carrying mosquitoes are established.

For Florida, the latest outbreak is another reminder that a disease long associated with international travel can also emerge locally when the right combination of infected people, mosquitoes and weather conditions comes together.