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Imported Dengue -- United States, 1995

Dengue is an acute disease caused by any of four mosquito-transmitted virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4) and characterized by the sudden onset of fever, headache, myalgias, rash, nausea, and vomiting. The disease is endemic in most tropical areas of the world and can occur in U.S. residents returning from travel to such areas. This report summarizes information about imported dengue among U.S. residents during 1995 and documents a substantially increased incidence of dengue in the Caribbean, Central America, and Mexico.

Serum samples from 441 persons who had suspected dengue with onset in 1995 were submitted to CDC for diagnostic testing from 31 states and the District of Columbia. Of these, 79 (18%) cases from 21 states were serologically or virologically diagnosed as dengue by isolation of dengue virus, detection of anti-dengue immunoglobulin M, single high titers of immunoglobulin G antibodies in acute serum samples, or a fourfold or greater rise in dengue-specific antibodies between acute- and convalescent-phase serum samples (1). Seven additional cases with laboratory-positive dengue were reported by the Texas Department of Health (TDH), all of which were diagnosed at a commercial reference laboratory (Table_1).

Of the 281 suspected cases reported from Texas, most (200 {71%}) resulted from intensified surveillance by the TDH because of an epidemic of dengue in the adjoining state of Tamaulipas, Mexico (2). More samples than usual also were received from residents of Oregon and travelers to Tortola (British Virgin Islands). Cases of dengue were diagnosed among a group of disaster-relief workers from Oregon who traveled to St. Thomas, U.S. Virgin Islands, in September following hurricanes Luis and Marilyn. Serum samples were requested from all travel companions of one patient with laboratory-diagnosed dengue who traveled to Tortola in August.

Of the 86 persons with laboratory-diagnosed dengue, 44 (51%) were female. Ages were reported for 54 persons and ranged from 1 year to 73 years (median: 40 years). The virus serotype (DEN-1, DEN-2, and DEN-3) was identified for five cases (Table_1). Based on travel histories available for 81 persons, infections probably were acquired in the Caribbean islands (48 cases), Mexico and Central America (24), Asia (five), South America (three), and Africa (one).

Clinical information was available from 54 patients with laboratory-diagnosed cases. The most commonly reported symptoms were consistent with classic dengue fever (e.g., fever {100%}, headache {70%}, myalgias {55%}, and rash {54%}). Of the 29 patients with rash, in 13 (45%) the rash was described as maculo-papular. Other manifestations included skin hemorrhages, petechiae, or purpura (nine cases); low platelet counts (20,000-134,000/mm3 {normal: 150,000-450,000/mm3}) (eight); low white blood cell counts (1000-2700/mm3 {normal: 3200-9800/mm3}) (six); and elevated liver enzymes (six). At least 11 patients were hospitalized.

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

Editorial Note

Editorial Note: In the Americas, dengue is transmitted by Aedes aegypti mosquitoes. Although nearly eradicated from the region in the 1960s, this species is now present in most tropical areas of the Americas and is present year-round in the southernmost areas of Florida and Texas; a small focus also exists on the island of Molokai, Hawaii. Autochthonous transmission of dengue occurred in the United States during 1980, 1986, and 1995; the seven cases in Texas in 1995 were laboratory diagnosed (by serologic testing and the isolation of DEN-2 and DEN-4 virus serotypes) among persons who did not travel outside Texas (2,3). Although most cases of dengue are characterized by mild manifestations, infection in some persons can result in the more severe forms of the disease -- dengue hemorrhagic fever (DHF) (fever, platelet count less than or equal to 100,000/mm3, hemorrhagic manifestations, and a leaky capillary syndrome {evidenced by hemoconcentration, hypoalbuminemia, or pleural or abdominal effusions}) or dengue shock syndrome (DSS) (DHF plus hypotension or narrow pulse pressure {less than or equal to 20 mm Hg}) (4). The fatality rate for patients with DSS can be as high as 44% (5), compared with 1%-2% for patients with appropriately treated DHF.

The incidence of dengue and DHF is increasing in the Americas. In 1995, dengue outbreaks were reported from many countries in Central America and the Caribbean (6,7). As a result, the number of laboratory-diagnosed cases reported to CDC in 1995 was larger than the average annual number (n=45) during 1987-1994. This increase especially reflects the impact of active surveillance in Texas initiated in August 1995 and the occurrence of cases among the group of travelers to Tortola and in the group of disaster-relief workers from Oregon.

The cases among disaster-relief workers and persons who traveled to Tortola underscore the importance of prevention measures for susceptible persons who travel to areas with endemic disease. These measures include avoidance of exposure to mosquitoes (8) through use of mosquito repellent and protective clothing at all times. Although mosquito activity is greatest in the early morning and in the late afternoon, mosquitos may feed at any time during the day, especially indoors, in shady areas, or during overcast periods. Ae. aegypti may be present in dark areas in domestic settings (e.g., closets, bathrooms, behind curtains, and under beds). The risk for exposure to dengue may be lower for tourists in some settings, including beaches and heavily forested areas and jungles.

Health-care providers should consider dengue in the differential diagnosis for all patients who have fever and a recent (i.e., preceding 2 weeks) history of travel to tropical areas. When dengue is suspected, patients should be monitored for evidence of hypotension, hemoconcentration, and thrombocytopenia. Because of the anticoagulant properties of acetylsalicylic acid (i.e., aspirin), only acetaminophen products are recommended for management of fever. Acute- and convalescent-phase serum samples should be obtained for viral isolation and serodiagnosis and sent for confirmation through state or territorial health departments to CDC's Dengue Branch, Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, 2 Calle Casia, San Juan, PR 00921-3200; telephone (787) 766-5181; fax (787) 766-6596. Serum specimens should be accompanied by a summary of clinical and epidemiologic information, including a detailed travel history with dates and location of travel and dates of onset of illness and blood collection.


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

  2. CDC. Dengue fever at the U.S.-Mexico border, 1995-1996. MMWR 1996;45:841-4.

  3. Hafkin B, Kaplan JE, Reed C, et al. Reintroduction of dengue fever into the continental United States. I. Dengue surveillance in Texas, 1980. Am J Trop Med Hyg 1982;31:1222-8.

  4. Pan American Health Organization. Dengue and dengue hemorrhagic fever: guidelines for prevention and control. Washington, DC: Pan American Health Organization, 1994:12-3.

  5. Tassniyom S, Vasanawathana S, Chirawatkul A, Rojanasuphot S. Failure of high-dose methylprednisolone in established dengue shock syndrome: a placebo-controlled, double-blind study. Pediatrics 1993;92:111-5.

  6. Briseňo-GarcŠa B, Gýmez-Dantes H, Argott-RamŠrez E, et al. Potential risk for dengue hemorrhagic fever: the isolation of serotype dengue-3 in Mexico. Emerging Infectious Diseases 1996;2:133-5.

  7. World Health Organization. Dengue and dengue haemorrhagic fever. Martinique World Epidemiological Record 1996;71:195.

  8. CDC. Advisory memorandum no. 109 -- dengue update. Atlanta: US Department of Health and Human Services, Public Health Service, March 10, 1995.

Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 1. Suspected and laboratory-diagnosed cases of imported dengue, by state -- United States, 1995
                            Laboratory-      Travel history, if known, of persons with laboratory-
State           Suspected     diagnosed      diagnosed dengue (serotype, if known)
Alabama                 2             0
Arizona                 2             0
California              4             1       Tortola
Colorado                7             0
Connecticut             1             1       Tortola
District of             1             1       Eritrea
Florida                 5             3       Honduras, "Virgin Islands," Ecuador
Georgia                13             5       Haiti, Jamaica (2 cases), Puerto Rico, Tortola
Hawaii                  2             1       Taiwan
Illinois                1             1       Puerto Rico
Iowa                    1             0
Indiana                 1             0
Maryland                4             2       St. John, Tortola
Massachusetts          12             8       Anguilla, Jamaica, Puerto Rico, Tortola (2 cases)
Michigan                5             2       Tortola, Thailand (DEN-2)
Missouri                3             3       Haiti (2 cases), Puerto Rico and U.S. Virgin Islands
Mississippi             1             0
Montana                 2             0
North Carolina          7             2       Honduras (DEN-3), Indonesia
Nebraska                1             0
New Mexico              1             0
New York               23            12       "Caribbean," Dominican Republic (2 cases), Haiti, Honduras,
                                              St. Thomas, (DEN-1), Thailand, Tortola (3 cases)
Ohio                    8             4       Haiti, Nicaragua, Tortola (2 cases)
Oregon                 36             8       Aruba and Venezuela, St. Thomas (7 cases)
Pennsylvania            2             2       Barbados (DEN-2), Tortola
Rhode Island            1             0
South Carolina          2             1       Tortola
Texas                 281            22       Caribbean, El Salvador, Guatemala, Honduras (2 cases),
                                              Mexico (13 cases), Mexico and El Salvador (DEN-3), Puerto
                                              Rico and Grenada (2 cases), Tortola
Utah                    2             0
Vermont                 3             2       St. Thomas, Tortola
Washington              5             1       India
Wisconsin               9             4       Costa Rica, St. Croix and Puerto Rico, Nicaragua, Venezuela

Total                 448            86

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