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Imported Dengue -- United States, 1991

Serum samples from 82 persons with suspected imported dengue (1) who had onset in 1991 were submitted to CDC from 27 states and the District of Columbia (Table 1, page 731). Of these, 25 (34%) cases (from 18 states) were serologically or virologically diagnosed as dengue. This report summarizes these cases.

The dengue serotype was identified by virus isolation in two of the cases. Travel histories were available for all persons with laboratory-diagnosed dengue (Table 1, page 731); 11 cases were acquired in Asia, seven in the Caribbean islands, four in Central America, and one each in Tahiti and an unspecified location in Latin America; one person acquired dengue during travel to Australia and Thailand.

Of the 25 persons with laboratory-diagnosed dengue, sex was reported for 23; 12 were female. Age was reported for 22 and ranged from 20 to 61 years (median: 32.5 years). Date at onset of symptoms -- reported for 24 persons -- was from June through September for 11 persons and in January or December for five. For persons with laboratory-diagnosed dengue, the most commonly reported symptoms were consistent with classic dengue fever (e.g., fever, rash, headache, and myalgia). At least four persons required hospitalization; 10 patients developed low white blood cell counts (1500-4400/mm3), and seven patients had low platelet counts (15,000-145,000/mm3).

Reported by: State and territorial health departments. Dengue Br, Div of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Although most dengue infections result in mild illness, some may cause the severe form of the disease -- dengue hemorrhagic fever -- characterized by fever, low platelet count (less than or equal to 100,000/mm3), hemorrhagic manifestations, and leaky- capillary syndrome evidenced by hemoconcentration, hypoalbuminemia, or pleural or abdominal effusions (2).

In the Americas, dengue is transmitted by the Aedes aegypti mosquito. Although nearly eradicated from the region in the 1960s, this species is now found in all tropical countries of the region except Bermuda, the Cayman Islands, and Costa Rica and is present year-round in the southernmost areas of Texas and Florida. Ae. albopictus, a vector of dengue viruses in Asia and recently introduced and established in the United States, is widely distributed in many states in the eastern half of the country, where introduced cases of dengue are detected annually (3).

Although endemic transmission of dengue has not occurred in the United States since 1986 (south Texas), introduction of the virus by international travelers could result in local transmission. The 82 cases referred for serologic confirmation in 1991 represent the lowest number of reports since 1984 (63 cases), and a 20% decrease from 1990 (102 cases), but do not include cases of dengue reported to state health departments without accompanying specimens for testing.

Dengue is endemic in many islands in the Caribbean, Mexico, and most countries in Central and South America. Three of the four serotypes (DEN-1, DEN-2, and DEN-4) have been circulating in the region since 1981. Although transmission of DEN-3 has not been detected since 1977, it could be reintroduced by travelers. During 1989-1991, DEN-3 was isolated from U.S. residents returning from Africa and the South Pacific.

Most persons with laboratory-diagnosed cases in 1991 had onset of symptoms during popular months for travel. Tourists should avoid exposure to mosquitoes in tropical locations. Because Aedes species that transmit dengue may bite at any time during the day, with peak activity in the early morning and late afternoon, the use of mosquito repellent and protective clothing is recommended.

Physicians should consider dengue in the differential diagnosis for all patients who present with compatible manifestations and have a history of travel to tropical areas. Acetaminophen products are recommended for management of fever to avoid the anticoagulant properties of acetylsalicylic acid (i.e., aspirin). Acute and convalescent (up to 30 days after onset of symptoms) serum samples should be obtained for viral isolation or serodiagnosis.

Suspected dengue cases should be reported to state health departments along with a clinical summary, dates at onset of illness and blood collection, and epidemiologic information, including a detailed travel history with dates and locations of travel. Acute and convalescent serum samples should be sent for confirmation through the state health department laboratory to the Dengue Branch, Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, CDC (2 Calle Casia, San Juan, PR 00921-3200); telephone (809) 749-4400; fax (809) 749-4450.


  1. CDC. Case definitions for public health surveillance. MMWR 1990;39(no. RR-13):10-1.

  2. World Health Organization. Dengue haemorrhagic fever: diagnosis, treatment, and control. Geneva: World Health Organization, 1986:12-

  3. Moore CG, Francy DB, Eliason DA, Bailey RE, Campos EG. Aedes albopictus and other container-inhabiting mosquitoes in the United States: results of an eight-city survey. J Am Mosq Contr Assoc 1990;4:173-8.

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