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Dengue is
a mosquito-borne disease caused by a flavivirus. Dengue fever usually
results in the abrupt onset of high fever, headache, myalgias, arthralgias,
lymphadenopathy, and a rash that appears with a 2nd temperature
rise after an afebrile period. Respiratory symptoms, such as cough,
sore throat, and rhinorrhea, can occur. Dengue can also cause potentially
fatal hemorrhagic fever with bleeding tendency and shock. Diagnosis
involves PCR and serologic testing. Treatment is symptomatic, including
meticulously adjusted intravascular volume replacement.
Dengue is endemic to the tropical regions of the world in latitudes from about 35° north to 35° south. Outbreaks are most prevalent in Southeast Asia but also occur in the Caribbean, including Puerto Rico and the US Virgin Islands, Oceania, and the Indian subcontinent; more recently, dengue incidence has increased in Central and South America. Each year about 100 to 200 cases are imported to the US by returning tourists. The causative agent, a flavivirus with 4 serogroups, is transmitted by the bite of Aedes mosquitoes.
Symptoms and Signs
After an incubation period of 3 to 15 days, chills, headache, retro-orbital pain with eye movement, lumbar backache, and severe prostration begin abruptly. Extreme aching in the legs and joints occurs during the first hours, which accounts for the traditional name of breakbone fever. The temperature rises rapidly to up to 40° C, with hypotension and relative bradycardia. Bulbar and palpebral conjunctival injection, a transient flushing or pale pink macular rash, particularly of the face, and a palpable spleen are common. Cervical, epitrochlear, and inguinal lymph nodes are usually enlarged.
Fever and other symptoms persist 48 to 96 h, followed by rapid defervescence with profuse sweating. Patients then feel well for about 24 h, after which fever usually occurs again, typically with a lower peak temperature than the first. Simultaneously, a blanching maculopapular rash spreads from the extremities to cover the body diffusely except the face or to cover the trunk and extremities in a patchy distribution. The palms and soles may be bright red, swollen, and itchy.
Mild cases of dengue, usually lacking lymphadenopathy, remit in < 72 h. In more severe disease, asthenia may last several weeks. Death is rare. Immunity to the infecting strain is long-lasting, whereas broader immunity to other strains lasts only 2 to 12 mo.
Diagnosis
Dengue fever is suspected in patients in endemic areas who develop sudden fever, headache, myalgias, and adenopathy, particularly with the characteristic rash or recurrent fever. Evaluation should rule out alternative diagnoses, especially malaria and leptospirosis. Diagnostic studies include PCR of blood and serology. Serology involves hemagglutination inhibiting or complement fixation tests using paired sera, but cross-reactions with other flavivirus antibodies are possible. Although rarely performed, cultures can be done using mosquitoes or specialized cell lines. CBC may show leukopenia by the 2nd day of fever; by the 4th or 5th day, the WBC count may be 2000 to 4000/μL with only 20 to 40% granulocytes. Urinalysis may show moderate albuminuria and a few casts.
Treatment
and Prevention
Treatment is symptomatic. People in endemic areas should try to prevent mosquito bites. To prevent further transmission by mosquitoes, patients with dengue should be kept under mosquito netting until the 2nd bout of fever has resolved. Vaccines are being evaluated.
Dengue Hemorrhagic
Fever
(Philippine, Thai, or Southeast Asian Hemorrhagic Fever;
Dengue Shock Syndrome)
Dengue hemorrhagic fever (DHF) is a variant presentation that occurs primarily in children < 10 yr living where dengue is endemic. DHF requires prior exposure to the dengue virus. It is an immunopathologic disease.
DHF is suspected in children with World Health Organization (WHO)–defined clinical criteria for the diagnosis: sudden fever that stays high for 2 to 7 days; hemorrhagic manifestations, including at least a positive tourniquet test and petechiae, purpura, ecchymoses, bleeding gums, hematemesis, or melena; and hepatomegaly. The tourniquet test is performed by inflating a BP cuff to midway between the systolic and the diastolic BP for 15 min. The number of petechiae that form within a 2.5-cm diameter circle are counted; > 20 petechiae suggests capillary fragility. Shock may ensue. CBC, coagulation tests, urinalysis, liver function tests, and dengue serologic tests should be obtained. Thrombocytopenia (< l00,000 platelets/μL) and a prolonged PT characterize the coagulation abnormalities. There may be mild proteinuria and increases in AST levels. Complement fixation antibody titers against flaviviruses are usually high. Patients with WHO-defined clinical criteria plus thrombocytopenia (≤100,000/μL) or hemoconcentration (Hct increased by ≥20%) are presumed to have the disease.
In adults, DHF begins with abrupt fever and headache and is initially indistinguishable from classic dengue. Shock and increasing illness may develop rapidly 2 to 6 days after onset. 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 can occur.
Mortality ranges from 6 to 30%; most deaths occur in infants. Patients require intensive treatment to maintain euvolemia. Both hypovolemia (which can produce shock) and overhydration (which can produce acute respiratory distress syndrome) should be avoided. Urine output and the degree of hemoconcentration can be used to monitor intravascular volume. No antivirals have been shown to improve outcome.
Last full review/revision November 2005
Content last modified November 2005
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