The number of dengue cases reported in the United States in 2024 was 359% higher than the annual average reported from 2010 through 2023, according to a study published last week inMorbidity and Mortality Weekly Report. The increase was driven almost entirely by infections acquired during international travel amid a surge in dengue cases that year.
Of the 3,798 cases reported in the United States in 2024, 97.2% were linked to travel, with most tied to destinations in the Caribbean, including Puerto Rico and the US Virgin Islands (34.1%). Travel to North America—primarily Mexico—accounted for 24.3% of infections, and travel to Central America for 15.6%. Locally acquired cases accounted for 2.8% of the overall US case count.
Florida reported the most cases overall, with 1,044 infections, followed by California with 720 and New York with 338. Locally acquired infections were identified in Florida, California, and Texas, with Florida accounting for 85 of the 105 locally acquired cases (81%) reported nationwide.
The sharp rise in US cases mirrors a worldwide surge. Infections globally climbed to 14.1 million in 2024, an increase of roughly 8 million cases in 2023.
More areas become endemic
Spread by Aedes aegypti and Aedes albopictus mosquitoes, dengue is the leading cause of febrile illness (illness characterized by fever) in travelers returning to the United States from areas where the virus is endemic. Severe illness can be marked by heavy bleeding, respiratory distress, and organ impairment.
Ae aegypti and albopictus mosquitoes are found throughout large areas of the southeastern and southwestern United States and continue to spread to other regions of the country. Roughly half of US counties have mosquito species that can transmit viruses to humans, and the climate in three quarters of the country is amenable to Aedes species, the report notes.
Vector presence and distribution might be further affected by increasing temperatures, which can expand the range of mosquitoes that spread dengue.
The authors warn that climate change could be a growing factor in dengue’s spread. “Vector presence and distribution might be further affected by increasing temperatures, which can expand the range of mosquitoes that spread dengue, enhance vector survival, and change the reproduction and biting rates,” the authors write.
Need for prevention efforts, education
More than one-third of US dengue patients (36.1%) required hospitalization, and 105 met the criteria for severe dengue. Six deaths were reported. Adults ages 50 to 59 accounted for the largest proportion of infections and had the highest case-fatality rate.
The researchers note that most dengue cases occurred among patients reporting Hispanic ethnicity, potentially because Hispanic travelers may be more likely to visit dengue-endemic regions such as Latin America and the Caribbean, both heavily affected by outbreaks in 2024.
The authors say the record number of dengue cases reported in 2024 highlights the growing need for coordinated prevention and response efforts, including traveler outreach, community education, mosquito control, and increased clinical awareness of the possibility of dengue in patients with fever who have recently returned from endemic regions.
