Case study: Dengue Virus
A 30 year old woman presented to the clinic with fever, backache, and headache of two
days duration. She complained bitterly of intense myalgias in the uppers arms and pain
on moving her eyes. She had just returned form a trip to El Salvador, where she had
extensive exposure to mosquitoes. On physical examination she appeared uncomfortable,
but not toxic. A blanching erythematous rash was present on the face, arms, trunk, and
thighs. There was no enanthem, murmur, or splenomegaly. Her white blood count was
1,600/ul with a normal differential. Her platelet count was 140,000/ul and her
hemoglobin was 17.5 g/dl. Convalescent phase antibodies gave a positive result to
mosquito-borne dengue virus.
Questions and answers:
1. By what type of mosquito if this virus transmitted? Are any of these mosquitoes found
in the United States?
In the Western Hemisphere, the Aedes aegypti mosquito is the most important
transmitter. Nevertheless, a 2001 outbreak in Hawaii was transmitted by Aedes albopictus
(2). The mosquito is most frequently found in the tropics; it has some presence in the
southeastern United States (such as the lower half of Florida), but it seems to have been
competitively displaced by the introduction of Aedes albopictus (1).
2. Severe disease, which can be fatal, can occur with this infection. What are the clinical
manifestations of severe disease as a result of infection with this virus?
Dengue may appear as a potentially fatal disease called Dengue Hemorrhagic Fever
(DHF). The fever is usually accompanied by profuse sweating along with changes in
pulse rate and blood pressure.The clinical manifestations of DHF include: fever lasting 2-
7 days, petechial rash on extremities, enlargement of the liver(hepatomegaly), DSS that
is manifested by rapid and weak pulse, small capillaries become excessively permeable(
plasma leakage) that may lead to death if untreated.
3. There are four distinct serotypes of this virus. Would you predict that infection with
one serotype would confer immunity to the other serotypes?
It is known that dengue is caused by any of these four serotypes, known as, DEN-1,
DEN-2, DEN-3, and DEN-4.The viruses are defined based on their serological response.
In general a viral serotype is distinguished by protein or a protein component that
determines its antigenic specificity. In disease areas where multiple serotypes circulate
people often get secondary infections by a distinct serotype. Each virus serotype has
characteristics that influence the nature of dengue epidemic and disease severity. DEN-2
and DEN-3 are associated with severe dengue disease, while DEN-4 is primarily found in
secondary dengue. It is common to see more serious symptoms related to secondary,
rather than primary, infection. Immunity to the same serotype is long lasting, while
immunity to a serotype other than the one that caused the primary infection is at best
short lived. Based on the current information I predict that immunity to one of the four
serotypes would not confer resistance to one of the other three or to others that may arise
in the future. (3, 4)
4. In what geographic range is this disease endemic? What means can be taken by
travelers to endemic regions to prevent infection?
The disease is endemic in the tropics; Asia, Pacific Islands, Central and South America,
Carribean, and Africa. To prevent infections, travelers should: use mosquito repellents
containing DEET, use mosquito nets, spray insecticides, wear protective clothing such as
long sleeves and pants, and avoid being outdoors during feeding times of the Aedes
aegypti mosquitoes which is usually in the morning and late afternoon.
2. Division of Vector-Borne Infectious Diseases. Dengue and Dengue Hemorrhagic
3.Gubler, Duane J. (1998) Dengue a Dengue Hemorrhagic Fever. Clin Microbiol Rev.
4. Nisalak Ananda et al. (2003) Serotype-Specific dengue Virus Circulation And Dengue
Disease In Bangkok, Thailand From 1973-1999. 68(2):191-202
5. Rothman L.Alan. Dengue: a research perspective.