(See the World
Health Organization's web site for a map
of countries with moderate to high risk of
Dengue presents an extreme risk to travelers
in the tropics and sub-tropics, and according
to the Centers for Disease Control, its global
distribution is comparable to that of malaria.
A small risk of dengue also exists in the southeastern
part of the U.S. The risk of infection is higher
in urban areas, and limited to altitudes below
600 m (2000 ft.).
Dengue is caused by any one of four distinct
virus strains transmitted through the bite of
Aedes aegypti, the same mosquito that transmits yellow
fever. This mosquito bites during the day.
Infection with one strain does not produce immunity
to other strains, and people can have four dengue
infections in their lifetime.
Symptoms of dengue include a sudden, high fever
(which may occur in two waves), accompanied by
extreme muscle pain and headache. A rash develops
three to four days after initial symptoms appear.
The symptoms can continue for several days and
the only treatment is bed rest and fluids, with
fever-reducing medication. This form of dengue
is not life threatening.
Dengue hemorrhagic fever (DHF) is another form
of dengue but far more dangerous, as it causes
uncontrolled internal bleeding and has a 5 percent
fatality rate. On rare occasions, dengue shock
syndrome occurs as a result of DHF, with a fatality
rate of up to 50 percent if it is not treated
There is no vaccine against dengue and no available
medicine to prevent or treat it. The only defense
against dengue and DHF is avoiding mosquito bites.