21-09: Dengue Fever

Clinical Summary

Dengue fever, also known as “breakbone fever,” is a mosquito-borne viral disease. A flavivirus, dengue is a rapidly emerging illness due to reintroduction of Aedes species mosquitoes into areas of previous eradication. It is now distributed throughout tropical and subtropical regions, and widespread epidemics have occurred in the Caribbean and Southeast Asia, among other world regions. Dengue is one of the most common causes of fever in returning travelers.

The incubation period is usually 3 to 7 days, with symptom resolution within 10 days. Infection ranges from subclinical symptoms to a hemorrhagic state with possible shock. Most commonly, it is characterized by fever, severe myalgias, retro-orbital pain, and headache. A rash, seen in approximately half of patients, is usually maculopapular, but may be mottled, flushed, or petechial. The recently revised classification of dengue severity consists of dengue without warning signs, dengue with warning signs, and severe dengue based on the degree of plasma leakage, spontaneous bleeding, organ impairment, and shock.

There are four serotypes; exposure to one serotype provides lifelong immunity to that type. Previous infection with one serotype may predispose an individual to a more severe infection with another serotype. Thus, severe dengue is more common in indigenous individuals than the previously unexposed traveler. The diagnosis is primarily clinical. The presence of thrombocytopenia, leukopenia, and hemoconcentration is suggestive, and confirmatory tests with PCR or immunoglobulin M antibodies via enzyme-linked immunosorbent assay (ELISA) are available.

Management and Disposition

Supportive therapy is the only treatment available, with a focus on fluid repletion. Patients with mild illness are treated as outpatients. Admission of those with severe illness, hemorrhagic manifestations, shock, or an uncertain diagnosis is warranted.

Pearls

1. Consider dengue fever in recently returned travelers with fever, headache, and myalgias, particularly travelers from the Caribbean or Southeast Asia.

2. The fever tends to be high and may suddenly resolve and then return, also known as a “saddle back” fever pattern.

3. A positive “tourniquet test” is suggestive of dengue. A blood pressure cuff is applied and inflated to a point between the systolic and diastolic pressures for 5 minutes. The test is positive if there are more than 20 petechiae per square inch.

4. Occasional cases of dengue occur in South Texas, and an outbreak recently occurred in Key West, Florida.