A newly published report by V.I. Department of Health and CDC-affiliated authors documents 263 confirmed dengue cases, 15 hospitalizations and the U.S. Virgin Islands’ first confirmed dengue-associated death since 2005 during an outbreak spanning January 2024 through June 2025. The report also describes how the absence of local dengue testing initially required patient samples to be sent off-island, resulting in laboratory turnaround times of one to two months.
The findings were published October 15 in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report. The report examines the territory’s first dengue outbreak since 2012–2013, including barriers to testing, surveillance and clinical management, and the Department of Health’s response.
Its authors include territorial epidemiologist Dr. Esther Ellis and other Department of Health personnel, alongside CDC-affiliated contributors. First author Dr. Sarah Gallalee is listed with affiliations to both the V.I. Department of Health and CDC’s Epidemic Intelligence Service.
According to the report, St. Croix recorded the largest number of confirmed infections, with 118 cases, representing 45 percent of the territorywide total. St. Thomas accounted for 105 cases, or 40 percent, while St. John recorded 40 cases, representing 15 percent.
Fifteen patients were hospitalized, with stays averaging 4.3 days and ranging from two to 14 days. One patient, a 63-year-old woman with diabetes, died. The report identifies her death as the territory’s first confirmed dengue-associated fatality since 2005.
The outbreak investigation also found that 256 patients, representing 97 percent of confirmed cases, reported no travel during the two weeks preceding the onset of symptoms. That finding is consistent with transmission occurring predominantly within the territory rather than among people who had recently traveled elsewhere.
Patients ranged in age from two months to 89 years, with a median age of 44. Women accounted for 146 of the confirmed cases, or approximately 56 percent. Among 105 infections for which the dengue virus type was identified, 101 involved dengue virus type 2, while four involved type 3. Three of the four patients with type 3 infections reported recent travel to Puerto Rico.
Testing Barriers and Local Laboratory Improvements
During August and September 2024, the Department of Health and CDC conducted a surveillance evaluation and clinical needs assessment that identified two important barriers to detecting and managing dengue cases. Clinicians reported infrequent encounters with suspected dengue infections over the preceding decade and a need for training in clinical management, testing and disease reporting.
The assessment also found that no local diagnostic testing was available for dengue, requiring samples to be transported outside the Virgin Islands for analysis. According to the report, this produced turnaround times ranging from one to two months before test results were available.
The Department of Health introduced dengue diagnostic testing at the Territorial Public Health Laboratory in October 2024. The report states that the change reduced turnaround times to less than one week.
During fall 2024, the department also visited 30 clinics and conducted 20 clinical training sessions covering dengue management, testing and reporting. A telephone hotline was established in October to provide additional guidance to healthcare providers, while a web-based electronic disease-reporting platform was deployed during the fall.
The report does not specify how many patients experienced the longest testing delays or establish that those delays contributed to individual hospitalizations or the fatal case. Its discussion of one- to two-month turnaround times concerns conditions identified in 2024, before local testing began.
Outbreak Shifted Across the Territory
The report shows that the outbreak developed unevenly across the three islands, with St. Thomas and St. John recording most infections earlier in 2024 before cases increased sharply on St. Croix. Between July and September 2024, St. Thomas recorded 77 confirmed cases and St. John recorded 26, compared with six on St. Croix.
The pattern subsequently shifted. From October through December 2024, St. Croix recorded 64 confirmed infections, compared with five on St. Thomas and one on St. John.
St. Croix accounted for all 42 cases recorded during the first three months of 2025. Another five cases were reported on the island between April and June 2025, with no additional confirmed cases listed for St. Thomas or St. John during the first half of that year. The report places the territory’s annual dengue incidence at 2.5 cases per 1,000 residents in 2024.
Mosquito Control and Public Outreach
As infections spread, the Department of Health worked with CDC and the Puerto Rico Vector Control Unit on mosquito-control and public-education campaigns in affected communities. The response included door-to-door activities in 25 communities with reported dengue cases.
Teams inspected 256 residential yards for breeding sites associated with the Aedes aegypti mosquito, which transmits dengue, and applied mosquito larvicide at 167 households. Approximately 900 spatial-repellent devices were distributed. These devices release insecticide into the surrounding air without requiring electricity or heat.
The response also included distributing mosquito nets for cribs at seven childcare, orphanage and maternal and child healthcare facilities. Public education efforts reached 420 households and 54 schools, alongside activities at 10 public events and four press conferences.
The authors described the Department of Health’s response as encompassing local diagnostic testing, clinical training, mosquito-control interventions and public education. They emphasized maintaining those capabilities between outbreaks to support a rapid response to future increases in dengue infections.
Earlier Surveillance Findings
The Department of Health had publicly reported dengue case counts during the outbreak, and the Consortium previously covered the increase in infections during 2024 and into 2025. An October 28, 2024, department release, for example, reported 150 cases at that stage of the outbreak.
In an April 2026 examination of the department’s annual surveillance report, the Consortium reported that the territory recorded 47 confirmed dengue cases during calendar year 2025, alongside improvements to its electronic disease-surveillance system.
That annual figure and the 263 cases in the October publication cover different periods. The outbreak report’s table records 216 cases in 2024 and 47 during January through June 2025, totaling 263 across the 18-month period. Its first-half 2025 total matches the 47 cases reported for the full calendar year in the department’s annual report.
Correction: This article has been revised to clarify that the report was authored by V.I. Department of Health and CDC-affiliated researchers and published in CDC’s Morbidity and Mortality Weekly Report. It describes an outbreak investigation, not a separate federal inquiry. The reported case totals, death and testing delays remain unchanged.
