Problem/ConditionDengue is one of the most common vectorborne flaviviral infections globally,
with frequent outbreaks in tropical regions. In 2019 and 2020, the Pan
American Health Organization reported approximately 5.5 million dengue cases
from the Americas, the highest number on record. In the United States, local
dengue virus (DENV) transmission has been reported from all U.S.
territories, which are characterized by tropical climates that are highly
suitable forAedesspecies of mosquitoes, the vector that
transmits dengue. Dengue is endemic in the U.S. territories of American
Samoa, Puerto Rico, and the U.S. Virgin Islands (USVI). Dengue risk in Guam
and the Commonwealth of the Northern Mariana Islands is considered sporadic
or uncertain. Despite all U.S. territories reporting local dengue
transmission, epidemiologic trends over time have not been well
described.Reporting Period2010–2020.Description of SystemState and territorial health departments report dengue cases to CDC through
ArboNET, the national arboviral surveillance system, which was developed in
2000 to monitor West Nile virus infections. Dengue became nationally
notifiable in ArboNET in 2010. Dengue cases reported to ArboNET are
categorized using the 2015 Council of State and Territorial Epidemiologists
case definition. In addition, DENV serotyping is performed at CDC’s
Dengue Branch Laboratory in a subset of specimens to support identification
of circulating DENV serotypes.ResultsDuring 2010–2020, a total of 30,903 dengue cases were reported from
four U.S. territories to ArboNET. Puerto Rico reported the highest number of
dengue cases (29,862 [96.6%]), followed by American Samoa (660 [2.1%]), USVI
(353 [1.1%]), and Guam (28 [0.1%]). However, annual incidence rates were
highest in American Samoa with 10.2 cases per 1,000 population in 2017,
followed by Puerto Rico with 2.9 in 2010 and USVI with 1.6 in 2013.
Approximately one half (50.6%) of cases occurred among persons aged <20
years. The proportion of persons with dengue who were hospitalized was high
in three of the four territories: 45.5% in American Samoa, 32.6% in Puerto
Rico, and 32.1% in Guam. In Puerto Rico and USVI, approximately 2% of
reported cases were categorized as severe dengue. Of all dengue-associated
deaths, 68 (0.2%) were reported from Puerto Rico; no deaths were reported
from the other territories. During 2010–2020, DENV-1 and DENV-4 were
the predominant serotypes in Puerto Rico and USVI.InterpretationU.S. territories experienced a high prevalence of dengue during
2010–2020, with approximately 30,000 cases reported, and a high
incidence during outbreak years. Children and adolescents aged <20 years
were disproportionately affected, highlighting the need for interventions
tailored for this population. Ongoing education about dengue clinical
management for health care providers in U.S. territories is important
because of the high hospitalization rates reported. Dengue case surveillance
and serotyping can be used to guide future control and prevention measures
in these areas.Public Health ActionThe Advisory Committee on Immunization Practices recommends vaccination with
Dengvaxia for children aged 9–16 years with evidence of previous
dengue infection and living in areas where dengue is endemic. The
recommendation for the dengue vaccine offers public health professionals and
health care providers a new intervention for preventing illness and
hospitalization in the age group with the highest burden of disease in the
four territories (Paz Bailey G, Adams L, Wong JM, et al. Dengue Vaccine:
Recommendations of the Advisory Committee on Immunization Practices, United
States, 2021. MMWR Recomm Rep 2021;70[No. RR-6]). American Samoa, Puerto
Rico, and USVI are all considered endemic areas and persons residing in
these areas are eligible for the new dengue vaccine. Persons aged
9–16 years in those jurisdictions with laboratory evidence of
previous dengue infection can receive the dengue vaccine and benefit from a
reduced risk for symptomatic disease, hospitalization, or severe dengue.
Health care providers in these areas should be familiar with the eligibility
criteria and recommendations for vaccination to reduce the burden of dengue
among the group at highest risk for symptomatic illness. Educating health
care providers about identification and management of dengue cases can
improve patient outcomes and improve surveillance and reporting of dengue
cases.