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An acute febrile
disease of sudden onset with headache, fever, prostration, severe joint
and muscle pain, lymphadenopathy, and a rash that appears with a second
temperature rise after an afebrile period.
Epidemiology
Dengue is endemic
throughout the tropics and subtropics; outbreaks have occurred since
1969 in the Caribbean, including Puerto Rico and the U.S. Virgin
Islands. Cases have also been imported in tourists returning from
Tahiti. The causative agent, a flavivirus with four distinct serogroups,
is transmitted by the bite of Aedes mosquitoes.
Dengue hemorrhagic
fever occurs primarily in children < 10 yr living where dengue is
endemic (most commonly Southeast Asia, China, and Cuba) and is
characterized by acute onset followed in several days by abdominal pain,
hemorrhagic manifestations, and circulatory collapse. It is also called
Philippine, Thai, or Southeast Asian hemorrhagic fever or dengue shock
syndrome.
Symptoms and Signs
After an
incubation period of 3 to 15 (usually 5 to 8) days, onset is abrupt with
chills, headache, retro-orbital pain on moving the eyes, lumbar
backache, and severe prostration. Extreme aching in the legs and joints
occurs during the first hours of illness. The temperature rises rapidly
to as high as 40° C (104° F), with relative bradycardia and
hypotension. The bulbar and palpebral conjunctivae are injected, and a
transient flushing or pale pink macular rash (particularly of the face)
usually appears. The spleen may be soft and slightly enlarged. Cervical,
epitrochlear, and inguinal lymph nodes are usually enlarged.
Fever and other
symptoms of dengue persist for 48 to 96 h, followed by rapid
defervescence with profuse sweating. This ushers in an afebrile period,
with a sense of well-being, that lasts about 24 h. A second rapid
temperature rise follows, usually with a lower peak than the first,
producing a saddle-back temperature curve. Cases have occurred without
the second febrile period. A characteristic maculopapular rash appears
simultaneously, usually spreading from the extremities to cover the
entire body except the face or distributed patchily over the trunk and
extremities. The palms and soles may be bright red and edematous. The
fever, rash, and headache and other pains constitute the dengue triad.
Mortality is nil in typical dengue. Convalescence often lasts several
weeks and is accompanied by asthenia. An attack produces immunity for
>= 1 yr. Atypical, mild cases of dengue, usually lacking
lymphadenopathy, remit after < 72 hrs.
In dengue
hemorrhagic fever, onset also is abrupt, with fever and headache.
However, rather than developing severe myalgia, lymphadenopathy, and a
rash, the child has respiratory and GI symptoms. Pharyngitis, cough,
dyspnea, nausea, vomiting, and abdominal pain are also present. Shock
(dengue shock syndrome) occurs 2 to 6 days after onset, with sudden
collapse or prostration, cool clammy extremities (the trunk is often
warm), weak thready pulse, and circumoral cyanosis. Bleeding tendencies
occur, usually as purpura, petechiae, or ecchymoses at injection sites;
sometimes as hematemesis, melena, or epistaxis; and occasionally as
subarachnoid hemorrhage. Hepatomegaly is common, as is bronchopneumonia
with or without bilateral pleural effusions. Myocarditis may be present.
Mortality for dengue hemorrhagic fever ranges from 6 to 30%; most deaths
occur in infants < 1 yr old.
Diagnosis
In dengue,
leukopenia is present by the 2nd day of fever; by the 4th or 5th day,
the WBC count has dropped to 2000 to 4000/µL with only 20 to 40%
granulocytes. Moderate albuminuria and a few casts may be found. Dengue
may be confused with Colorado tick fever, typhus, yellow fever, or other
hemorrhagic fevers. Serologic diagnosis may be made by hemagglutination
inhibiting and complement fixation tests using paired sera but is
complicated by cross-reactions with other flavivirus antibodies.
In dengue
hemorrhagic fever, hemoconcentration (Hct > 50%) is present during
shock; the WBC count is elevated in 1/3 of patients. Thrombocytopenia
(< l00,000/µL), a positive tourniquet test, and a prolonged
prothrombin time are characteristic and indicative of the coagulation
abnormalities. Minimal proteinuria may be present. AST levels may be
moderately increased. Serologic tests usually show high complement
fixation antibody titers against flaviviruses, suggestive of a secondary
immune response.
The WHO has
established clinical criteria for diagnosis of dengue hemorrhagic fever,
which is a medical emergency: acute onset of high, continuous fever that
lasts for 2 to 7 days; hemorrhagic manifestations, including at least a
positive tourniquet test and petechiae, purpura, ecchymoses, bleeding
gums, hematemesis, or melena; hepatomegaly; thrombocytopenia (<=
100,000/µL); or hemoconcentration (Hct increased by >= 20%). Those
with dengue shock syndrome also have a rapid weak pulse with narrowing
of the pulse pressure (<= 20 mm Hg) or hypotension with cold, clammy
skin and restlessness.
Prophylaxis and
Treatment
Dengue prophylaxis
requires control or eradication of the mosquito vector. To prevent
transmission to mosquitoes, patients in endemic areas should be kept
under mosquito netting until the second bout of fever has abated.
Treatment of dengue is symptomatic. Complete bed rest is important.
Aspirin should be avoided, but acetaminophen and codeine may be given
for severe headache and myalgia.
In dengue
hemorrhagic fever, the degree of hemoconcentration, dehydration, and
electrolyte imbalance must be evaluated immediately and monitored
closely for the first few days, since shock may occur or recur
precipitously.
Cyanotic patients should be given Oxygen.
Vascular collapse and
hemoconcentration require immediate, vigorous fluid replacement,
preferably with a crystalloid solution such as lactated Ringer's
solution; overhydration must be avoided. Plasma or human serum albumin
should also be given if there is no response in the first hour. Fresh
blood or platelet transfusions may control bleeding. Agitated patients
may be given paraldehyde, chloral hydrate, or diazepam. Hydrocortisone,
pressor amines, beta-adrenergic blocking agents, and vitamins C and K
are of doubtful value.
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