During the period 2010-2020, a total of 30,903 cases were reported to ArboNET from American Samoa, Guam, Puerto Rico and USVI; 21,705 (70.2%) were confirmed and 9,198 (29.8%) were probable (Table 1). The highest number of dengue cases occurred in people under the age of 20, accounting for about half (15,640 (50.6%)) of reported cases. The majority of cases occurred in males, accounting for 16,808 (54.4%) of all cases. About 2% (584) of all cases were classified as severe dengue. A total of 10,037 (32.4%) people with dengue were hospitalized and 68 (0.2%) deaths were reported. Travel to a country with local dengue transmission within 2 weeks of symptom onset was reported in 28 (0.1%) cases.
From 2010 to 2020, the majority (29,862 (96.6%)) of dengue cases were reported in Puerto Rico (Figure 1). The annual incidence per 1,000 population was highest during the two outbreaks of 2010 and 2013, 2.9 and 2.6, respectively (Figure 2). Of all reported cases in Puerto Rico, 20,675 (69.2%) were confirmed and 9,187 (30.8%) were probable; 54.6% of dengue cases were in men. About 50% of reported cases in Puerto Rico have occurred in people under the age of 20, with the 10-19 age group accounting for 37.3% of cases. The highest incidence and hospitalization rates were also seen in children aged 10-14 and 15-19 (Figure 3). In Puerto Rico, 32.6% of people with dengue were hospitalized and 68 dengue-associated deaths were reported between 2010 and 2020; the greatest number of deaths (n=10) occurred in people over the age of 70, although six (8.8%) of the deaths occurred in people under the age of 20 (Figure 4). Almost all (>99%) dengue cases in Puerto Rico were acquired locally.
From 2010 to 2020, American Samoa accounted for 660 (2.1%) of all cases reported in US territories (Figure 1). The annual incidence per 1,000 population was highest in 2017, reaching 10.2 per 1,000 population (Figure 2). All dengue cases were confirmed and 50.3% were female. The highest case numbers and rates occurred in people younger than 20; 68.0% of reported cases occurred in people under the age of 20 and 45.9% in people aged 10-19. The proportion of people hospitalized for dengue cases in American Samoa (45.5%) was similar to that in Puerto Rico (Table 1); the highest incidence rates and hospitalizations occurred in the 10-14 year and 15-19 year age groups (Figure 5). No dengue-associated deaths have been reported and one travel-related case has been reported.
US Virgin Islands
From 2010 to 2020, USVI accounted for 353 (1.1%) of all reported cases in US territories (Figure 1). The annual incidence per 1,000 population was highest during the 2012-2013 outbreak, with an annual incidence of 1.6 in 2013 (Figure 2). Almost all (96.9%) of the cases reported to the USVI were confirmed and 53.3% were in women. About a third of reported cases have occurred in children and adolescents under the age of 20, with the majority (21.5%) in the 10-19 age group. The 20 to 29 age group was the second most affected age group with 15.0% of cases. Three (0.8%) people with dengue were hospitalized and no dengue-associated deaths were reported. The highest incidence rate was observed in children aged 10 to 14 years (Figure 6). All reported cases were acquired locally.
During 2010-2020, Guam accounted for 28 (0.1%) of all reported cases in U.S. territories. All cases were confirmed and occurred in 2019 and 2020; however, almost half of all reported cases (13 (46.4%)) were travel-related. More than half (60.7%) of the cases involved men. As in other U.S. territories, the 10-19 age group has been hardest hit, with around 25% of reported cases. Unlike the other territories, the second most affected age group was people between the ages of 30 and 39, accounting for 21.4% of cases. Thirty-two percent of people with dengue were hospitalized and no dengue-associated deaths were reported (Table 1).
Distribution of Serovars in Puerto Rico, USVI and American Samoa
A total of 21,329 confirmed cases from Puerto Rico (21,194), USVI (119), and American Samoa (16) had DENV serotype data reported or performed by the CDC Dengue Branch Laboratory (Table 2). In Puerto Rico, the majority (72.9%) of cases were DENV-1, followed by DENV-4 (24.1%), which were associated with large dengue epidemics from 2010 to 2013 (Figure 7). Along with the emergence of chikungunya in 2014 and Zika in 2016, the overall number of dengue cases decreased from 2015 to 2019, with all four DENV serotypes circulating at low levels. In 2019 and 2020, dengue activity increased slightly, with all locally acquired cases being identified as DENV-1, in addition to multiple travel-associated DENV-2 and DENV-3 cases. In USVI, DENV-1 and DENV-4 were the two circulating dengue serotypes during the 2012–2013 outbreaks, with DENV-1 accounting for 80.7% of cases with available serotype. In American Samoa, limited serotype data were available, although cases of DENV-2 (n=2) and DENV-3 (n=14) were reported.