A newly published federal investigation has documented 263 confirmed dengue cases, 15 hospitalizations and the U.S. Virgin Islands' first confirmed dengue-associated death since 2005 during an outbreak that stretched from January 2024 through June 2025. The report also reveals that the territory initially lacked local dengue diagnostic testing, forcing patient samples to be sent off-island and resulting in laboratory turnaround times of one to two months.
The findings were published Thursday by the Centers for Disease Control and Prevention in its Morbidity and Mortality Weekly Report. The investigation, conducted with the V.I. Department of Health, examined the territory's first dengue outbreak since 2012–2013 and documented shortcomings in testing and clinical preparedness that health officials subsequently moved to address.
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 required hospitalization, with stays averaging 4.3 days and ranging from two to 14 days. One patient, a 63-year-old woman with diabetes, died. The CDC identified her death as the territory's first confirmed dengue-associated fatality in more than two decades.
The investigation also found that 256 patients, representing 97 percent of confirmed cases, reported no travel during the two weeks preceding the onset of symptoms. The finding indicates that the overwhelming majority of reported infections were associated with transmission within the territory rather than recent travel 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 Delays Exposed During Outbreak
Among the investigation's most consequential findings was the absence of local dengue diagnostic testing during the outbreak's early stages.
During August and September 2024, the CDC and Department of Health conducted a surveillance evaluation and clinical needs assessment that identified two major barriers to detecting and managing dengue cases. Healthcare providers reported limited experience treating suspected dengue infections over the preceding decade and a need for additional 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 CDC, this produced turnaround times ranging from one to two months before test results were available.
The Department of Health responded by introducing dengue diagnostic testing at the Territorial Public Health Laboratory in October 2024. The CDC reported 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 same period.
The CDC did not specify how many patients experienced the longest testing delays or determine whether those delays contributed to individual hospitalizations or the fatal case.
Outbreak Shifted Across the Territory
The report shows that the outbreak developed unevenly across the three islands, with St. Thomas and St. John recording the bulk of 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. During that same period, St. Croix recorded six.
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 remained the center of reported infections during the first three months of 2025, accounting for all 42 cases recorded during that period. 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 CDC reported that the territory's annual dengue incidence reached 2.5 cases per 1,000 residents in 2024.
Mosquito Control and Public Outreach
As infections spread, the Department of Health worked with the 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 small amounts of 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 healthcare facilities.
Public education efforts reached 420 households and 54 schools, alongside activities at 10 public events and four press conferences.
In their assessment, federal and territorial health officials concluded that the outbreak response had established local diagnostic testing, expanded clinical training and strengthened mosquito-control and public-education activities.
The CDC emphasized the need to maintain those capabilities between outbreaks so the Virgin Islands can respond quickly to future increases in dengue infections.
Earlier Surveillance Findings
The Consortium previously reported on the territory's dengue outbreak as infections increased during 2024 and continued into 2025.
In an April 2026 examination of the Department of Health's annual surveillance report, the Consortium reported that the territory recorded 47 confirmed dengue cases during calendar year 2025, alongside the modernization of its electronic disease-surveillance system.
The newly published CDC investigation provides a more detailed examination of the outbreak period, including the 263-case total, the confirmed fatality, island-by-island transmission patterns and the diagnostic delays identified in 2024.
The federal report covers cases through June 2025 and does not establish whether the territory's laboratory turnaround times and testing capacity have remained at the levels achieved after the October 2024 improvements.
