U.S. Virgin Islands recorded 263 dengue cases, its first outbreak since 2012

The U.S. Virgin Islands reported 263 confirmed dengue cases between January 2024 and June 2025, the territory's first dengue outbreak since 2012–2013, according to a field report published by the U.S. Centers for Disease Control and Prevention on 15 October 2026 [s1]. Annual incidence reached 2.5 per 1,000 population in 2024 [s1].

The cases were split across the territory's three main islands: St. Croix recorded 118 (45%), St. Thomas 105 (40%) and St. John 40 (15%) [s1]. Most illness clustered in the second half of 2024, with 109 cases having symptom onset in July–September and a further 70 in October–December [s1]. The median patient age was 44 years, and cases were spread fairly evenly across age bands: 42 (16.0%) were aged 17 or younger, 51 (19.4%) were 18–34, 52 (19.8%) were 35–49, 67 (25.5%) were 50–64, and 51 (19.4%) were 65 or older [s1]. Slightly more than half the patients were female — 146 (55.5%) versus 116 (44.1%) male, with one case of unknown sex [s1]. That broad age distribution, rather than a concentration in children or older adults, is consistent with a virus spreading through a population with little recent immunity.

One serotype dominated

Among the 105 cases with a known serotype, 101 (96%) were dengue virus type 2 (DENV-2) and four (4%) were DENV-3 [s1]. Three of the four DENV-3 cases reported recent travel to Puerto Rico, suggesting those were imported rather than locally acquired [s1]. The near-total dominance of a single serotype matters for what comes next. Infection with one dengue serotype confers lasting immunity to that serotype but not the others, and a later infection with a different serotype carries a higher risk of severe disease. An outbreak driven almost entirely by DENV-2 leaves a population with fresh immunity to DENV-2 — and potentially more exposed if another serotype arrives.

Severity and the single death

Fifteen patients (6%) were hospitalised, with an average stay of 4.3 days and a range of 2 to 14 days [s1]. There was one death, in a 63-year-old woman with diabetes — the territory's first confirmed dengue-associated death since 2005 [s1]. Diabetes and other chronic conditions are established risk factors for severe dengue, and the long gap since the last recorded death underscores how unusual a fatal outcome is in a setting where dengue circulates only intermittently.

Why the Caribbean is seeing more dengue

The outbreak fits a broader regional pattern. Dengue transmission across the Americas has surged in recent years, and territories such as the U.S. Virgin Islands — where the mosquito vector Aedes aegypti is established and where travel to and from higher-incidence areas is constant — are exposed both to locally driven waves and to imported cases that can seed new chains. The DENV-3 cases linked to Puerto Rico travel are a small but concrete example of how movement around the Caribbean can introduce serotypes a population has not recently seen.

The report carries the usual limits of outbreak surveillance. The 263 figure counts confirmed cases, which undercounts true infection because many dengue infections are mild or asymptomatic and never reach a laboratory. Serotype was established for only 105 of the cases, so the DENV-2 dominance, while striking, rests on a subset [s1]. The concentration of onsets in the second half of 2024 — 109 in July through September and 70 in October through December — also means the outbreak was effectively a single season's wave with a long reporting tail rather than sustained transmission across the full 18 months [s1]. And a field report documents what happened rather than forecasting what follows.

What it establishes is that a place which had gone more than a decade without a dengue outbreak, and two decades without a dengue death, recorded both in a single 18-month stretch. For a population now carrying substantial DENV-2 immunity, the risk that shapes the next season is less a repeat of this wave than the arrival of a different serotype — the classic set-up for the more severe disease that dengue can cause on second infection. The practical levers are unchanged: mosquito control, early recognition of warning signs, and surveillance fast enough to catch the next serotype shift when it comes.

This article is informational and is not medical advice.