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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.
References
CDC. Imported dengue fever--United States, 1984. MMWR
1985;34:488-9.
Hayes GR, Scheppf PP, Johnson EB. An historical review of the
last
continental U.S. epidemic of dengue. Mosq News 1971;31:422-7.
Gubler DJ. Current research on dengue. Curr Topics in Vector
Res
1987;3:37-56.
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.
CDC. Update: Aedes albopictus infestation--United States. MMWR
1986;35:649-51.
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