Florida is experiencing its largest dengue outbreak in decades, with state health officials reporting more than 250 locally acquired cases so far this year, predominantly in Hillsborough County, which includes Tampa. This marks the highest number of dengue cases recorded in a single calendar year in any continental U.S. state since at least the 1940s, according to available data from state health departments and medical literature.
Dengue is a mosquito-borne viral illness transmitted by Aedes species mosquitoes, which thrive in warm climates like Florida’s. While many infected individuals remain asymptomatic, the disease can cause high fever, severe muscle and joint pain—earning it the nickname "breakbone fever"—and in severe cases, hemorrhaging, shock, and death. Florida has reported one fatality this year, involving an elderly woman from Tampa who died in early September.
The disease is caused by four distinct virus types (1 through 4), and immunity to one does not guarantee protection against the others. Secondary infections can sometimes result in more severe symptoms due to a phenomenon known as antibody-dependent enhancement, complicating efforts to develop an effective vaccine. Most residents in the Tampa area lack prior immunity to these viruses, increasing susceptibility, according to Dawn Wesson, an expert on mosquito-borne diseases at Tulane University.
The mosquitoes responsible for spreading dengue have expanded their geographical range in the U.S. in recent years, a trend linked to climate change. While these mosquitoes have become more widespread in southern parts of the country, including Southern California, Florida remains the primary hotspot for locally transmitted cases. Historically, most U.S. dengue infections were travel-related, with local transmission limited to places like Puerto Rico and isolated outbreaks in southern Florida. The last significant local outbreak in Florida occurred in Key West in 2009-2010, after several decades without cases.
The current outbreak in the Tampa region, which emerged publicly in July, is approaching the scale of a 2015-2016 dengue outbreak in Hawaii that reported 264 locally acquired cases. Nationwide, the Centers for Disease Control and Prevention (CDC) has recorded nearly 1,900 local dengue cases this year, the majority of which have occurred in Puerto Rico. Globally, the World Health Organization has documented more than 2.2 million infections and nearly 1,200 deaths from dengue in 2026.
State and local officials in Hillsborough and neighboring counties have declared local emergencies and intensified mosquito control efforts, including continuous spraying operations to reduce mosquito populations. Despite the outbreak’s severity, Florida officials have not requested deployment of CDC disease investigators, though the agency has provided $800,000 in funding assistance.
Public health experts emphasize the importance of personal protective measures to reduce the risk of infection, especially since the Aedes mosquitoes can bite throughout the day. Recommended precautions include applying Environmental Protection Agency-approved insect repellents containing DEET, wearing long-sleeved clothing, and staying indoors in air-conditioned or screened environments.
The surge in dengue cases in the Tampa area may be linked partly to travel patterns, as Florida receives many visitors and returning residents from endemic regions such as Puerto Rico. As local transmission continues, health officials urge residents to remain vigilant to curtail the outbreak’s spread.