Travel-Associated Dengue Cases — United States, 2010–2021

Results

During 2010–2021, a total of 7,528 confirmed or probable travel-associated dengue cases were reported to ArboNET. Among these, 1,474 (20%) occurred in 2019, representing a 168% increase over the annual average of 550 cases during 2010–2018 and 2020–2021, and a 61% increase over the 913 cases reported in 2016, the year with the second highest number of cases (Figure 1). The lowest annual number of cases reported (205) was in 2021, when travel patterns were substantially altered because of the COVID-19 pandemic. During all three analysis periods, cases were evenly distributed among females and males, and age distribution remained consistent, with median ages of 41, 42, and 42 years during 2010–2018, 2019, and 2020–2022, respectively (Table).

The proportions of cases classified as dengue-like illness, dengue, and severe dengue were similar in 2019, 2010–2018, and 2020–2021. The proportions of cases among patients who were hospitalized and who had an unknown disposition were similar during 2010–2018 (42% and 2%, respectively) and in 2019 (42% and 5%, respectively), whereas a smaller proportion of patients was hospitalized (33%) and a higher proportion had an unknown disposition (22%) during 2020–2021. Fewer than 1% of dengue patients died during 2010–2018 (18) and in 2019 (one), and no deaths occurred during 2020–2021. DENV-1 was the most frequently reported type across the three periods; however, the dengue type was unknown for 95% of cases during 2010–2018, 93% in 2019, and 83% during 2020–2021.

During the entire period, most cases (90%) were associated with travel outside U.S. states or territories. The most frequently visited region among travel-associated cases in 2019 was the Caribbean (39%), followed by Asia (27%) and North America^§§§ (14%). Travel patterns were similar during 2010–2018, with 33%, 29%, and 10% of patients reporting travel to those three regions, respectively. However, during 2020–2021, a period with major disruptions to travel because of the COVID-19 pandemic, the most frequently visited region was North America (30%), followed by the Caribbean (27%) and Asia (19%). The number of dengue cases per million air trips to destinations outside North America or Europe in 2019 (41.9 per million) was nearly twice that during other years during 2010–2021 (21.0 per million). These rates varied by region of travel across the periods analyzed. During 2010–2018, the highest number of cases per million air trips was associated with travel to Central America (32.1), followed by Asia (22.9) and the Caribbean (20.5). (Figure 2) (Supplementary Table 1, https://stacks.cdc.gov/view/cdc/131003). In 2019, the highest rates were associated with travel to the Caribbean (56.8), Central America (49.7), and Asia (39.6); during 2020–2021, the highest number of cases per million trips (37.3) was associated with travel to Oceania, followed by Asia (23.5) and South America (15.8).

Travelers returning from the top 10 countries of acquisition during 2010–2021 accounted for more than two thirds (69%) of cases reporting an international travel history (Supplementary Figure; https://stacks.cdc.gov/view/cdc/131002). Seven countries (Cuba, the Dominican Republic, El Salvador, India, Jamaica, Mexico, and the Philippines) were among the top 10 countries of acquisition across all three periods (Supplementary Table 2, https://stacks.cdc.gov/view/cdc/131004). Seasonality among travel-associated cases was similar during 2010–2018 and 2019, with most cases occurring during July–November. Seasonal trends were less apparent during 2020–2021, when fewer cases were reported relative to previous periods.