Florida's dengue outbreak hits 252 cases, largest in the continental US in decades

Florida has recorded 252 locally acquired dengue cases so far this year — the most reported by any state in the continental United States in a single calendar year since at least the 1940s, according to state health officials. The number has already surpassed Florida's own previous annual record of just under 200 cases set in 2023, and is closing in on the 264 locally acquired cases Hawaii reported over six months in 2015 and 2016, the largest outbreak by any U.S. state in recent decades.

The outbreak is concentrated in Hillsborough County, home to Tampa, which accounts for 223 of the state's more than 250 local infections. That geography has puzzled public health experts: dengue cases in Florida have historically clustered around Miami and South Florida, not Tampa. Hillsborough, Pasco, and Pinellas counties have all declared local states of emergency, with Hillsborough extending its declaration through October 8. Fogging crews are working day and night in neighborhoods including South Tampa, Davis Islands, and Harbor Island.

One person has died. An elderly Tampa woman — reported by CiberCuba as 80 years old — died on September 4, marking Florida's first dengue-related death this year. The outbreak first came to light in July and has continued to grow since.

For the first time this year, locally transmitted cases have outpaced travel-associated ones: 252 locally acquired versus 245 travel-linked, according to state data. At least 13 of the Hillsborough County cases did involve people who had recently traveled, but the broader pattern indicates the virus is circulating steadily among the local population rather than being reseeded entirely by returning travelers.

Dengue is caused by a virus spread primarily through bites from Aedes aegypti and Aedes albopictus mosquitoes, both present in Florida. Symptoms range from none at all to sudden fever, severe headache, pain behind the eyes, and intense muscle and joint pain — a combination so debilitating the disease has earned the nickname 'breakbone fever.' Most people recover, but severe cases can cause bleeding, shock, and death.

The disease's biology makes it particularly tricky. There are four types of dengue virus. A first infection builds lifelong immunity against that specific type — but if someone is later infected with a different type, antibodies from the first infection can actually help the new virus enter immune cells and replicate, worsening the second illness. That mechanism has made developing an effective vaccine difficult, and there is currently no dengue vaccine recommended for the general public in the continental U.S.

Most people in the Tampa area don't have prior immunity to any form of dengue.— Dawn Wesson, Tulane University dengue expert

That lack of prior immunity makes the Tampa population especially vulnerable, Wesson told the Los Angeles Times. She also noted that travel patterns may partly explain why the outbreak has taken hold in Tampa rather than Miami, though the precise reasons remain unclear.

The federal response has been limited. The CDC has provided $800,000 in emergency funding to the Florida health department and is monitoring the outbreak, but has not sent disease investigators — because Florida officials have not requested them, according to CDC spokesperson Jason McDonald. Wesson noted that the CDC's traditionally visible role in such outbreaks has been absent this time.

The outbreak is unfolding against a backdrop of record global dengue activity. More than 2.2 million infections and nearly 1,200 deaths have been reported worldwide this year, according to the World Health Organization, with the true toll likely higher because mild or asymptomatic cases often go untested. In the U.S., there have been nearly 1,900 locally acquired cases this year, the vast majority in Puerto Rico, which consistently sees far higher totals than any of the 50 states.

Climate conditions are a factor in the longer-term picture. The warm-weather mosquitoes that transmit dengue have been expanding their geographic range, and have become widespread in Southern California in recent years, according to the LA Times. Local transmission has also occurred in Texas, Hawaii, Arizona, and California in addition to Florida.

There's a good chance that this is the new normal.— Dawn Wesson, Tulane University dengue expert

For people in affected areas, the CDC recommends using EPA-registered insect repellents containing active ingredients such as DEET, wearing loose-fitting long-sleeved shirts and long pants, staying indoors behind screens or in air-conditioned spaces, and eliminating any standing water around their homes — including in old tires or bottle caps — where mosquitoes breed. The virus-carrying mosquitoes can bite at any time of day, though they are most active just after sunrise and around sunset.

Why it matters — The outbreak signals that locally transmitted dengue — long considered a rare, travel-linked anomaly in the continental US — may be becoming a recurring seasonal threat as mosquito ranges expand and more communities lack prior immunity.

Reported by thehill.com, independent.co.uk, latimes.com, en.cibercuba.com