Florida's Dengue Outbreak Reaches 252 Local Cases, the Largest in the Continental U.S. in Decades

Florida has now recorded 252 locally acquired dengue cases in 2026, making the Tampa Bay-centered outbreak the largest in any U.S. state in a single calendar year since at least the 1940s, according to state health data and an Associated Press review of state records and medical journals. Hillsborough County accounts for 223 of those cases, one Tampa woman has died, and three Tampa Bay counties have declared local emergencies to step up mosquito control.

The figures come from the Florida Department of Health's weekly arbovirus surveillance report covering Sept. 20 to 26, which added 62 locally acquired cases in a single week. One week earlier, the state count stood at 190.

Where the Cases Are

Locally acquired cases are infections in people who caught dengue from a mosquito in Florida rather than while traveling. The state counts them by county of exposure. The latest report lists cases in seven counties:

By date of illness onset, 21 cases began in July, 150 in August and 81 in September, according to the report. Of the 232 local cases tested to identify the virus type, nearly all were dengue serotype 2, including 206 in Hillsborough. Miami-Dade's cases included both serotype 2 and serotype 3.

The September figure will likely grow, because cases are added by onset date as lab results and investigations are completed.

How It Compares

Florida's previous worst year was 2023, when just under 200 locally spread cases were reported, according to the AP. The largest outbreak in any U.S. state since the 1940s had been in Hawaii, where 264 locally acquired cases were reported over six months spanning 2015 and 2016. Florida's 2026 total is already the most for any state within a single calendar year in that span, with the mosquito season still underway.

Before 2009, when cases appeared in Key West, dengue had not been transmitted locally in the continental U.S. outside the Texas-Mexico border since 1945.

Travel-related cases remain high as well. The state has recorded 245 travel-associated dengue cases in 2026, 150 of them in Miami-Dade County residents, and 201 of those travelers were exposed in Cuba, according to the surveillance report. Hillsborough has recorded 13 travel-associated cases. Health officials watch travel cases closely because an infected traveler bitten by a local mosquito can start a chain of local transmission.

One Death

The outbreak has caused one death: an elderly Tampa woman who died on Sept. 4, according to the AP. Most dengue infections cause no symptoms or a flu-like illness with fever, headache, pain behind the eyes, muscle and joint pain and rash. A small share progress to severe dengue, which can cause bleeding and shock. People who have had dengue before face a higher risk of severe illness if infected with a different serotype.

Emergencies and Mosquito Control

Pasco, Hillsborough and Pinellas counties declared local states of emergency in the week of Sept. 21, giving county administrators power to speed up mosquito control spending and seek state and federal reimbursement. Hillsborough County Administrator Bonnie Wise signed an order on Oct. 1 extending her county's emergency to Oct. 8, and Pinellas extended its order to the same date. WUSF reported that Pasco also remains under an emergency.

The state surveillance report found dengue virus in 20 mosquito pools in 2026, 19 of them in Hillsborough, including three positive samples of Aedes aegypti collected Sept. 22 and Sept. 24. Hillsborough County said its traps in many neighborhoods are showing dengue virus activity in mosquito populations, and its Mosquito Management Services crews have increased treatments by air and ground.

On the nights of Oct. 1 and Oct. 2, a county helicopter applied the insecticide Dibrom over South Tampa, Davis Islands and Harbor Island at an altitude of about 150 feet. The Lee County Mosquito Control District sent four helicopters and crews to help with daytime larvicide missions, with each helicopter carrying up to 200 gallons per trip, WUSF reported. Lee County's mosquito control communications director told the station that mosquito control agencies join forces because mosquitoes don't know boundaries.

County officials said the daytime treatments target larvae, the nighttime treatments target adult mosquitoes, and both are approved by the U.S. Environmental Protection Agency.

The Centers for Disease Control and Prevention has provided $800,000 to the Florida Department of Health for the response, CDC spokesman Jason McDonald told the AP, but federal disease investigators must be invited by the state, and Florida officials have not asked for them.

Advisories Beyond Tampa Bay

As of the state's most recent listing, dated Aug. 29, Alachua, Duval, Hillsborough, Miami-Dade, Orange, Pasco and Pinellas counties were under a mosquito-borne illness alert, the higher of two levels, while Brevard, Leon, Palm Beach, Polk and Walton counties were under an advisory. Some of those designations also reflect West Nile virus activity. Orange and Polk confirmed their locally acquired dengue cases in late September.

How to Protect Yourself

The mosquito that spreads dengue, Aedes aegypti, lives close to people and lays eggs in small containers of standing water, such as buckets, plant saucers, birdbaths and old tires. It bites mainly during the day. The Department of Health's long-running Drain and Cover message asks residents to:

• Drain standing water around the home at least once a week, including in gutters, pool covers, pet dishes and tires.
• Cover skin with long sleeves and pants and use an EPA-registered repellent such as DEET, picaridin, IR3535 or oil of lemon eucalyptus.
• Cover doors and windows with intact screens and use air conditioning when possible.

Hillsborough residents can drop off up to 12 tires a year for free at county community collection centers with proper identification, and Pinellas and Pasco are offering similar tire programs through October, WUSF reported. Anyone who develops a fever after mosquito bites should see a health care provider and mention possible dengue exposure.

What's Next

The Department of Health publishes its arbovirus surveillance report weekly, and the next update will show whether the pace of new cases is slowing after the jump of 62 in late September. Hillsborough's and Pinellas' emergency orders run through Oct. 8 unless extended again. Mosquito activity typically declines as temperatures cool later in the fall, but Tulane University expert Dawn Wesson told the AP that there's a good chance that this is the new normal.