|
Dengue is transmitted by
the bite of an Aedes mosquito infected with any one of the four
dengue viruses. It occurs in tropical and sub-tropical areas of the
world. Symptoms appear 3—14 days after the infective bite. Dengue
fever is a febrile illness that affects infants, young children and
adults.
Symptoms range from a mild fever, to incapacitating high fever, with
severe headache, pain behind the eyes, muscle and joint pain, and
rash. There are no specific antiviral medicines for dengue. It is
important to maintain hydration. Use of acetylsalicylic acid (e.g.
aspirin) and non steroidal anti-inflammatory drugs (e.g. Ibuprofen)
is not recommended.
Typically, people
infected with dengue virus are asymptomatic (80%) or only have mild
symptoms such as an uncomplicated fever.Others have more severe
illness (5%), and in a small proportion it is life-threatening. The
incubation period (time between exposure and onset of symptoms)
ranges from 3–14 days, but most often it is 4–7 days. Therefore,
travelers returning from endemic areas are unlikely to have dengue
if fever or other symptoms start more than 14 days after arriving
home. Children often experience symptoms similar to those of the
common cold and gastroenteritis (vomiting and diarrhea), but are
more susceptible to the severe complications.
Dengue haemorrhagic fever (fever, abdominal pain, vomiting,
bleeding) is a potentially lethal complication, affecting mainly
children. Early clinical diagnosis and careful clinical management
by experienced physicians and nurses increase survival of patients.
In some people, the
disease proceeds to a critical phase, which follows the resolution
of the high fever and typically lasts one to two days. During this
phase there may be significant fluid accumulation in the chest and
abdominal cavity due to increased capillary permeability and
leakage. This leads to depletion of fluid from the circulation and
decreased blood supply to vital organs. During this phase, organ
dysfunction and severe bleeding, typically from the gastrointestinal
tract, may occur. Shock (dengue shock syndrome) and hemorrhage
(dengue hemorrhagic fever) occur in less than 5% of all cases of
dengue, however those who have previously been infected with other
serotypes of dengue virus ("secondary infection") are at an
increased risk.
The recovery phase occurs next, with resorption of the leaked fluid
into the bloodstream. This usually lasts two to three days. The
improvement is often striking, but there may be severe itching and a
slow heart rate. During this stage, a fluid overload state may
occur; if it affects the brain, it may cause a reduced level of
consciousness or seizures.
Treatment of acute
dengue is supportive, using either oral or intravenous rehydration
for mild or moderate disease, and intravenous fluids and blood
transfusion for more severe cases. The incidence of dengue fever has
increased dramatically since the 1960s, with around 50–100 million
people infected yearly. Early descriptions of the condition date
from 1779, and its viral cause and the transmission were elucidated
in the early 20th century.
Dengue has become a
global problem since the Second World War and is endemic in more
than 110 countries. Apart from eliminating the mosquitoes, work is
ongoing on a vaccine, as well as medication targeted directly at the
virus.
|
