A resident of Hillsborough County, Florida, has been diagnosed with dengue fever, marking the first instance of the virus being transmitted within the United States this year. The individual had not traveled outside of Florida, indicating local transmission.
Dengue fever is a mosquito-borne illness that can cause severe joint and muscle pain, often described as "breakbone fever." While many infections are asymptomatic, some cases can lead to life-threatening internal bleeding, respiratory distress, heart failure, shock, and organ failure.
The primary vector for dengue fever in the U.S. is the Aedes aegypti mosquito, identifiable by white bands on its legs. This mosquito species nearly vanished from the U.S. in the 1970s following eradication efforts, but sporadic outbreaks have resurfaced, particularly in Florida and California, after these campaigns were discontinued.
Most dengue cases recorded in the U.S. are typically linked to international travel. However, the recent case in Hillsborough County, one of Florida's most populous counties with approximately 1.5 million residents, raises concerns about domestic transmission. Experts suggest the virus could enter the country if infected mosquitoes stow away on ships or if an infected traveler is bitten by a local Aedes mosquito, which then spreads the virus to others.
In 2025, Florida recorded 71 locally acquired dengue cases, with additional cases reported in California and Arizona. Since 2010, over 600 cases of dengue fever have been diagnosed in individuals who had not recently left the country.
In response to the rise in dengue cases globally, the Centers for Disease Control and Prevention (CDC) has updated its travel alerts. The agency has identified a higher-than-expected number of dengue cases among U.S. travelers returning from 11 countries and territories: Bolivia, Cambodia, Colombia, Kenya, Malaysia, Maldives, New Caledonia, Samoa, Sri Lanka, Tonga, and Vietnam. The CDC urges travelers to these regions to take precautions.
Public health officials recommend protective measures for individuals in dengue-prone areas, including wearing insect repellent, covering skin with long-sleeved shirts and long pants when outdoors, and sleeping in air-conditioned rooms or rooms with intact window screens. Children under five, adults over 65, and pregnant women are considered at higher risk for severe complications from dengue fever.
Symptoms of dengue fever, which typically appear five to seven days after infection, can include a fever above 100°F (38°C), severe headache, pain behind the eyes, and pain in bones, joints, or muscles. A rash may also develop a few days after the fever subsides. There is no specific cure for dengue fever; treatment focuses on managing symptoms and complications through supportive care, such as hydration and pain relief with acetaminophen. Severe cases may require hospitalization for intensive monitoring and treatment.
A three-dose dengue vaccine is available and recommended for children aged nine to 16 years, offering approximately an 80 percent reduction in the risk of symptomatic infection.