Travel-associated Dengue Surveillance — United States, 2006–2008

R Luce, DVM; A Rivera, MS; H Mohammed, PhD; KM Tomashek, MD; Dengue Br; J Lehman

Disclosures

Morbidity & Mortality Weekly Report. 2010;59(23):715-719. 

In This Article

Editorial Note

During 2006–2008, an average of 244 confirmed and probable travel-associated dengue cases were identified by ArboNET or CDCDB annually (Figure), compared with an annual average of 33.5 cases (range:13–77 cases) identified during 1990–2005. Most of this increase likely resulted from the 2003 addition of dengue reporting to the ArboNET surveillance system, which supplements CDCDB.[6] However, a portion of the increase also likely resulted from substantial increases in dengue incidence throughout subtropical and tropical areas of the world, including the Americas.[6] During 2006–2008, dengue outbreaks were reported in numerous countries, including Belize, Brazil, Costa Rica, Cuba, Ecuador, El Salvador, Guadeloupe, India, Madagascar, Martinique, Mexico, Nicaragua, Pakistan, Paraguay, the United States (Puerto Rico, U.S. Virgin Islands), Venezuela, and multiple island nations in the South Pacific. Most U.S. residents become infected during travel to tropical and subtropical areas outside the continental United States, although autochthonous transmission has been documented on multiple occasions since 1980 in Texas,[7,8] during 2001–2002 in Hawaii,[9] and during 2009–2010 in Florida.[10]

Figure.

Number and incidence of laboratory-confirmed cases* per 100 million U.S. travelers — combined ArboNET and CDC Dengue Branch (CDCDB), 1996–2008
* Based on 1996–2005 data from CDCDB, and 2006–2008 data from the CDCDB and ArboNET electronic surveillance system.
Source: Office of Travel and Tourism Industries. 2007 United States resident travel abroad. Washington, DC: US Department of Commerce, International Trade Administration, Office of Travel and Tourism Industries; 2008. Available at http://www.tinet.ita.doc.gov/outreachpages/download_data_table/2007_us_travel_abroad.pdf.

Dengue has an incubation period of 3–14 days. Because U.S. travelers spend a median of 10 nights abroad, many returning travelers who are infected could be viremic and able to infect endemic Aedes spp. vector mosquitoes (principally Ae. aegypti and Ae. albopictus) in some locations in the continental United States, thus creating the potential for localized dengue transmission. Clinically recognized cases of travel-associated dengue likely underestimate the risk for importation because many dengue infections are asymptomatic or mildly symptomatic (Box).

The findings in this report are subject to at least three limitations. First, these surveillance results likely are subject to underreporting because both CDCDB and ArboNET are based on passive reporting (i.e., each rely on public health jurisdictions and health-care providers to detect and report infection) and dengue was designated a nationally notifiable disease in the United States in 2010, after the ending date of this report. Second, cases submitted to ArboNET were classified as either probable or laboratory-confirmed by the reporting jurisdiction largely based on interpretation of laboratory results from private laboratories using several different laboratory diagnostic tests, which might have affected classification and reporting of results. Finally, travel histories and clinical information were not available for all cases and might not have been representative of all persons with travel-associated dengue.

Travelers to tropical areas can reduce their risk for dengue by avoiding exposure to mosquitoes. No vaccine is available for preventing dengue infection. Persons traveling to areas where dengue is endemic should use insect repellents, wear protective clothing, and reside in facilities with screens and air conditioning when available. Preventing travel-associated dengue not only benefits the traveler, but also helps prevent the introduction of dengue virus into tropical areas and subtropical areas of the United States (primarily the southeastern states), where vector mosquitoes could transmit the virus indigenously.

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