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Epidemiologic Notes and Reports Imported and Indigenous Dengue Fever -- United States, 1986

In 1986, 233 cases of dengue-like illness were reported to CDC from 32 states (Table 1). Adequate blood samples were received on 120 cases, 33 (27%) of which were confirmed as dengue infection. These 33 confirmed cases were reported from 10 states and the District of Columbia (Figure 1).

Virologic or serologic evidence indicated that three serotypes, DEN-1, DEN-2, and DEN-4, were imported into the United States in 1986. Seventeen (52%) of the confirmed cases were reported from two states (Texas and Georgia) where Aedes aegypti may be found during most of the year. Twenty cases (61%) occurred in five states where an exotic mosquito species, Aedes albopictus, has recently become established (Illinois, Indiana, Ohio, Texas, and Georgia).

In 1986, Texas had the first known indigenous transmission of dengue in the United States in 6 years. The last known indigenous transmission had also occurred in Texas. Five of the 14 cases from Texas that were confirmed by CDC were probably imported. Nine of the patients, however, had no history of travel outside of Texas, suggesting that the infections were acquired locally (Laredo, 2 cases; Corpus Christi, 3 cases; and Brownsville, 4 cases). Two DEN-1 viruses were isolated, one from an individual without travel history outside of Texas and the other from a patient who had traveled to Monterrey, Mexico, just prior to onset of illness. Three blood samples (0.9%) from a random sample of 315 patients from venereal disease clinics in southern Texas were positive for dengue-specific IgM antibodies, indicating dengue infection within the previous 2-3 months.

Although the majority of imported dengue cases were reported as dengue fever without hemorrhagic manifestations, one patient, who had traveled to the Dominican Republic, required hospitalization with petechiae, purpura, and thrombocytopenia. As in previous years, travel histories of persons with confirmed dengue showed that most cases were imported from Caribbean basin and Asian countries (Table 1). Reported by: Holy Redeemer Hospital, Meadowbrook, Pennsylvania. Georgia Dept of Human Resources, Atlanta, Georgia. Illinois Dept of Public Health, Chicago. Indiana State Board of Health, Bur of Laboratories, Indianapolis. Michigan Dept of Public Health, Lansing. Minnesota Dept of Health, Minneapolis. New York Dept of Health, New York. Office of Medical Svcs, Dept of State, Washington, DC. Ohio Dept of Health, Columbus. State of California Dept of Health Svcs, Berkeley. State Laboratory Institute, Jamaica Plain, Massachusetts. Texas Dept of Health, Austin. Dengue Br, Div of Vector-Borne Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Since 1977, 1,561 suspected dengue cases have been reported to CDC; 327 were positive for dengue (Table 2). Since 1981, all four dengue virus serotypes have been imported (1). The annual number of reported and confirmed cases of dengue imported into the United States varies with the amount of dengue activity occurring in the tropics, especially the Caribbean (2). The number of reported dengue cases in 1986 was the highest in recent years and coincided with increased dengue activity throughout the Americas.

Transmission in 1986 was of particular concern for two reasons. First, indigenous transmission occurred in Texas for the second time in 6 years--the last previous transmission prior to 1980 had occurred in 1945 (2). Second, confirmed dengue cases were reported in areas where Ae. aegypti and Ae. albopictus, two efficient vectors of dengue, occur. The recent introduction of Ae. albopictus into the United States is of special concern because this species is an exceptionally efficient host for dengue viruses and is capable of transmitting both horizontally (human to human) and vertically (from infected female to her offspring) (3,4). Moreover, Ae. albopictus has become established in northern as well as southern states (5). The presence of this species increases the potential for more widely distributed secondary transmission and for the maintenance of dengue viruses in the United States. CDC is currently collaborating with state health departments to improve surveillance for both the introduction of dengue virus and for the presence of the mosquito vectors.

Dengue should be considered in the differential diagnosis of acutely ill persons returning to the United States from any tropical region of the world. It should also be remembered that dengue can be clinically similar to measles and should be considered when patients test negative for measles. Blood samples should be obtained from such patients during both the acute and convalescent stages of illness and should be submitted without delay to appropriate state or local public health laboratories for serologic and virologic diagnostic studies. In addition, a clinical summary with dates of onset of illness and blood collection, a detailed travel history with dates of travel, and other epidemiologic data should be included.


  1. CDC. Imported dengue fever--United States, 1984. MMWR 1985;34:488-9.

  2. Hayes GR, Scheppf PP, Johnson EB. An historical review of the last continental U.S. epidemic of dengue. Mosq News 1971;31:422-7.

  3. Gubler DJ. Current research on dengue. Curr Topics in Vector Res 1987;3:37-56.

  4. Rosen L, Shroyer DA, Tesh RB, Freier JE, Lien JC. Transovarial transmission of dengue viruses by mosquitoes: Aedes albopictus and Aedes aegypti. Am J Trop Med Hyg 1983;32: 1108-19.

  5. CDC. Update: Aedes albopictus infestation--United States. MMWR 1986;35:649-51.

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