Dengue Fever
Dengue is primarily a disease of the
tropics, and the viruses that cause
it are maintained in a cycle that
involves humans and Aedes aegypti,
a domestic, day-biting mosquito that
prefers to feed on humans. Infection
with dengue viruses produces a spectrum
of clinical illness ranging from a
nonspecific viral syndrome to severe
and fatal hemorrhagic disease. Important
risk factors for dengue hemorrhagic
fever include the strain and serotype
of the infecting virus, as well as
the age, immune status, and genetic
predisposition of the patient.
The first reported epidemics of dengue fever occurred in 1779-1780 in Asia, Africa, and North America; the near simultaneous occurrence of outbreaks on three continents indicates that these viruses and their mosquito vector have had a worldwide distribution in the tropics for more than 200 years. During most of this time, dengue fever was considered a benign, nonfatal disease of visitors to the tropics. Generally, there were long intervals (10-40 years) between major epidemics, mainly because the viruses and their mosquito vector could only be transported between population centers by sailing vessels.
A global pandemic of dengue began
in Southeast Asia after World War
II and has intensified during the
last 15 years. Epidemics caused
by multiple serotypes (hyperendemicity)
are more frequent, the geographic
distribution of dengue viruses and
their mosquito vectors has expanded,
and dengue hemorrhagic fever has
emerged in the Pacific region and
the Americas. In Southeast Asia,
epidemic dengue hemorrhagic fever
first appeared in the 1950s, but
by 1975 it had become a leading
cause of hospitalization and death
among children in many countries
in that region.
|
