Dengue is the world’s leading mosquito-borne viral disease and can be fatal without proper treatment. Four related dengue virus types cause it, spread by Aedes mosquitoes; infection gives lasting immunity only to the type caught. Worldwide, dengue causes approximately 400 million infections a year, a quarter of them with symptoms, and more than 40,000 deaths. In the U.S. states, most cases follow travel to places where dengue is common, though it spreads locally in six U.S. territories and freely associated states.
A record year
Dengue became nationally notifiable in 2010. From 2010 to 2021, 7,528 confirmed or probable travel-related cases were reported to CDC’s ArboNET surveillance system.
- 2019 brought 1,474 cases — 20% of the total, 168% above the average of about 550 a year in the other years, and 61% above the previous high of 913 in 2016. That mirrored a global surge: the World Health Organization reported more dengue cases in 2019 than ever before.
- 2021 had the fewest, 205, as COVID-19 upended travel.
- Relative to air travel beyond North America and Europe, 2019 saw 41.9 cases per million trips, against 21.0 in other years.
Travel-associated dengue cases reported in the United States, 2010–2021. Image from CDC’s report.
Who got sick
Cases were evenly split between women and men, with median ages of 41–42 throughout. About 42% were hospitalized in 2010–2018 and in 2019 (33% in 2020–2021). Fewer than 1% died: 18 in 2010–2018 and one in 2019, with none in 2020–2021. DENV-1 was the most commonly reported type, though the type was unknown for most cases.
Where travelers caught it
About 90% of cases followed travel outside U.S. states and territories.
| Period | Top regions of travel |
|---|---|
| 2010–2018 | Caribbean 33%, Asia 29%, North America 10% |
| 2019 | Caribbean 39%, Asia 27%, North America 14% |
| 2020–2021 | North America 30%, Caribbean 27%, Asia 19% |
Per million air trips, the riskiest regions were Central America in 2010–2018 (32.1), the Caribbean in 2019 (56.8), and Oceania in 2020–2021 (37.3). The top 10 countries of acquisition accounted for 69% of cases with international travel; Cuba, the Dominican Republic, El Salvador, India, Jamaica, Mexico and the Philippines were in the top 10 in every period. Most cases occurred July through November.
What it means
Dengue is expected to spread further, raising the risk to travelers. Clinicians should consider it in returning travelers with fever, because:
- prompt recognition and intravenous fluids cut deaths to under 1%, while untreated dengue can kill up to 13%
- infected travelers can bring the virus home to Aedes mosquitoes, present in half of U.S. counties, starting local spread
A dengue vaccine is recommended for children 9–16 with confirmed past infection who live where dengue is endemic in the U.S. — but not for travelers. Travelers should prevent mosquito bites: EPA-registered repellent, protective clothing, and lodging with air conditioning or window screens.
Limits: many travelers with dengue are never tested or correctly diagnosed, severe cases may be undercounted, a 2015 change in case definitions complicates comparisons, and cases not reported to U.S. surveillance are missing.
Sources
Based on Wong JM, Rivera A, Volkman HR, et al., "Travel-Associated Dengue Cases — United States, 2010–2021," MMWR Vol. 72, No. 30, CDC; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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