‘Breakbone fever’ is surging worldwide as mosquitoes expand into new territories

The Tampa Bay Times reported the death of an elderly woman on Sept. 8, 2026. Her family says local doctors attributed her death to dengue fever, although the Florida Department of Health has not yet confirmed that.

This death was likely part of a larger dengue outbreak in Hillsborough County, where there have been 95 documented cases of dengue since July 2026. In August, the Hillsborough County Health Department issued a mosquito-borne illness alert due to reports of multiple locally acquired cases.

This cluster of locally spread cases is a stark reminder that a disease which most Americans associate with faraway tropical vacations is increasingly being caught at home.

Dengue is often called “breakbone fever,” and the nickname is earned. People who get sick typically develop a sudden high fever along with a pounding headache, pain behind the eyes and deep aches in the muscles, joints and bones. Many also feel nauseated, throw up or break out in a blotchy rash a few days in.

As an infectious diseases physician and tropical medicine specialist who directs a travel clinic, I see how easily dengue slips past both patients and doctors. In parts of the U.S. where the disease is still uncommon, it is easily mistaken for the flu or COVID-19, and that delay can be dangerous.

Dengue is not passed from person to person like a cold. It spreads through the bite of infected Aedes mosquitoes, mainly Aedes aegypti, a species commonly found in Florida. These mosquitoes thrive in warm cities and can breed in as little as a bottle capful of standing water. These mosquitoes bite during the day, not just at dusk.

The cycle is simple and hard to break: A mosquito bites an infected person, then bites someone else days later, giving them the virus.

Dengue is especially tricky because most infections cause no symptoms at all. Roughly 3 in 4 people who catch the virus never feel sick. For the 25% who are symptomatic, those symptoms don’t appear until four to 10 days after being bitten.

In addition, there are four different strains of the dengue virus, and surviving one gives you lasting protection against only that one. A second infection with a different type actually raises the odds of severe disease.

Most people suffer with dengue for a miserable week and then recover on their own. But about 1 in 20 patients progress to severe dengue, a life-threatening turn that tends to strike just as the fever breaks – often around days three to seven, when patients and their families may wrongly assume the worst is over.

In severe dengue, tiny blood vessels throughout the body start leaking fluid, blood pressure can crash and dangerous bleeding or organ damage can follow. Warning signs that someone is sliding into this phase include severe belly pain, repeated vomiting, bleeding from the gums or nose, extreme drowsiness or restlessness, and blood in vomit or stool.

Andrés Henao is a Professor of Medicine and Infectious Disease, University of Colorado Anschutz. This article was first published by The Conversation and is republished under a Creative Commons licence. Read the original article .