Record Dengue in the United States, 2024: Mostly From Travel, Some Local

Dengue is a mosquito-borne virus that can cause anything from mild illness to death, and it is a leading cause of fever in travelers coming home from places where it is endemic. Four types of the virus exist. Frequent or continuous spread in the United States is limited to six territories and freely associated states: American Samoa, Puerto Rico, the U.S. Virgin Islands, the Federated States of Micronesia, the Marshall Islands and Palau. Residents of the 50 states and the District of Columbia catch it mostly when they travel, although small numbers of locally acquired cases turn up where the right mosquitoes live.

From 2010 through 2023, an average of 828 cases a year (range 202–2,055) were reported from the states and DC to ArboNET, the national arboviral surveillance system. In 2024 the count reached a record 3,798, a 359% increase over that average. CDC researchers analyzed those cases, counting confirmed and probable cases with symptoms beginning in 2024; the numbers are preliminary.

Who got dengue, and where

• Source of infection: 3,693 cases (97.2%) followed travel outside the patient's home jurisdiction in the two weeks before illness; 105 (2.8%) were locally acquired.
• Timing: 1,581 cases (41.6%) began in July, August or September.
• Age and sex: the median age was 49. Adults aged 50–59 made up 21.8% of cases and those aged 40–49 made up 16%. Women accounted for 52.5%.
• Ethnicity: 57.5% of patients were Hispanic or Latino, as were 66.7% of those infected locally.
• States: Florida had the most cases (1,044), followed by California (720), New York (338) and Texas (241). Florida's rate, 4.47 per 100,000 people, was about four times the national rate of 1.12.
• Virus type: among the 1,204 cases where it was known, DENV-3 made up 54.8%, then DENV-4 (23.2%), DENV-1 (12.5%) and DENV-2 (9.5%).

Of travelers with a known destination, the most common were Mexico (892), Cuba (633) and India (225). By region, 34.1% of travel cases were acquired in the Caribbean, including Puerto Rico and the U.S. Virgin Islands; 24.3% in North America (Mexico and the United States); 15.6% in Central America; and 10.1% in Asia. Of 246 cases acquired in a U.S. state or territory, most came from Puerto Rico (76.4%) or the U.S. Virgin Islands (22.0%); both territories had outbreaks in 2024.

Travel-associated dengue cases by month of illness onset and region where the infection was acquired, 2024 (3,451 cases). Cases from South America were more common early in the year; those from the Caribbean, North America, Central America and Asia rose from July to November. CDC.

How serious it was

Most patients (95.8%) had dengue, 1.4% had dengue-like illness, and 105 (2.8%) had severe dengue, which can bring severe bleeding, plasma leakage and organ damage. More than a third of all patients (36.1%) were hospitalized, including 92 (88%) of those with severe dengue. Six people died, all of them travelers who developed severe dengue. Three of the deaths were among 829 patients aged 50–59, two among 578 aged 60–69, and one among 409 aged 20–29. The authors suggest the higher death rate in older adults may reflect more underlying health conditions.

Why the jump

The rise tracked a global surge. Worldwide, dengue cases reached 14.1 million in 2024, about 13 million of them in the Americas, roughly 8 million more than in 2023. The authors suggest the high share of Hispanic patients likely reflects more frequent travel to Latin America and the Caribbean, which had large outbreaks.

Locally acquired cases came from 10 counties in Florida (85 cases), three in California (18 cases) and two in Texas (two cases). Coming from several counties in each state, they point to many separate introductions rather than one lasting outbreak. None grew into a larger outbreak, but the authors see a rising risk: Aedes aegypti and Aedes albopictus mosquitoes, which can carry the virus, live in about half of U.S. counties, the climate in three quarters of the country suits them, and rising temperatures can widen their range and change how they survive, breed and bite.

The true number of infections is higher than reported. Many people have mild symptoms and never see a doctor, clinicians may not think to test, and reporting capacity varies from place to place.

Protecting travelers

No dengue vaccine is approved for U.S. travelers who visit, but do not live in, areas with dengue. Protection comes from preventing mosquito bites during the trip and after coming home, which also keeps the virus from reaching local mosquitoes:

• Use an EPA-approved insect repellent.
• Wear loose-fitting long sleeves and long pants.
• Stay where there is air conditioning or window screens.
• Empty standing water around the home so mosquitoes cannot lay eggs.

The authors urge clinicians to consider dengue in anyone with a fever who has returned from an affected area, to test for it, and to watch for signs that the illness is becoming severe: severe abdominal pain, persistent vomiting, bleeding from mucous membranes, or a change in mental state. They also call for messages tailored to Hispanic communities and travelers, stronger surveillance, and mosquito control where dengue is spreading.

Sources

• Kiplagat SJ, Rodriguez DM, Rivera A, Paz-Bailey G, Wong JM, Adams LE. Increase in Travel-Associated and Locally Acquired Dengue Cases — United States, 2024. MMWR Morb Mortal Wkly Rep 2026;75(18). https://www.cdc.gov/mmwr/volumes/75/wr/mm7518a1.htm
• CDC, dengue clinical management pocket guide: https://www.cdc.gov/dengue/hcp/pocketguide/index.html
• CDC, preventing dengue: https://www.cdc.gov/dengue/prevention/index.html