Dengue

Background

World map highlighting areas of dengue risk.

Femail Ades aegypti mosquito feeding on a person.

• A viral infection transmitted though Aedes mosquitos typically in urban areas, especially during rainy seasons in tropical/subtropic regions (Asia, Africa, Central America, Caribbean)
  • Los Angeles County reported 14 confirmed cases of locally acquired dengue in 2024
• Also known as "break-bone fever"
• Most infections are asymptomatic or produce only mild illness, but the virus occasionally causes more severe cases up to death (i.e., "severe dengue")
  • Severe dengue (which includes "dengue shock syndrome") is rare in travelers, as it is cause by a second infection of a different Dengue serotype (so patients must have had two separate exposures at different times to be at risk)

Clinical Features

Clinical course of dengue fever.

Early dengue rash.

Recover phase rash: classic islands of white in a sea of red.

Dengue

• Incubation 3-7 days
• Febrile phase:
  • High fever + "Break-bone" pain + GI symptoms + rash + possible exposure
  • +/- Faget sign
  • Lasts 3-7 days, majority recover

Severe Dengue

As above, followed by:

• Critical Phase:
  • Minority of patients, generally pediatric and elderly
  • Around time of defervescence
  • Vascular leak, hypoproteinemia, hemoconcentration, pleural effusion, ascites
  • Narrowed pulse pressure, persistent vomiting, RUQ tenderness, lethargy and restlessness are signs of impending collapse
  • Mucosal and skin bleeding

Differential Diagnosis

Fever in traveler

• Normal causes of acute fever!
• Malaria
• Dengue
• Leptospirosis
• Typhoid fever
• Typhus
• Viral hemorrhagic fevers
  • Ebola virus disease
  • Marburg virus disease
  • Lassa fever
  • Crimean-Congo hemorrhagic fever
• Chikungunya
• Yellow fever
• Rift valley fever
• Q fever
• Amebiasis
• Zika virus

Evaluation

Work-up

• Consider tests to rule out other possible processes:
  • CBC, chemistry, LFTs, viral panels
  • See Fever in traveler
• Definitive Dengue testing
  • Acute phase (0-7 days post symptom onset)
    • Nucleic acid amplification test (NAAT) (e.g., RT-PCR) OR NS1 ELISA test, AND
    • IgM antibody test
  • Convalescent Phase (>7 days post symptom onset)
    • IgM antibody (alone)
      • Can be reliably detected 3 months or longer after infection
• Concern for Severe Dengue
  • Add DIC labs

Diagnosis

When laboratory tests become positive. Day zero is symptom start. 1st = primary infection; 2nd = secondary infection.

• Typically a clinical diagnosis in the ED
  • All patients with clinically suspected dengue should receive appropriate management without waiting for diagnostic test results.
• Definitive testing
  • IgM diagnosed by a 4x increase in acute/ convalescent titers
• Other possible lab findings:
  • CBC: Leukopenia, thrombocytopenia, and hemoconcentration
  • CMP: LFTs elevated
  • DIC lab abnormalities
• Severe Dengue if any of the following identified:
  • Shock (from plasma leakage)
  • Hemorrhage
  • Respiratory distress

A positive NAAT test does not require further confirmatory testing. The presence of the dengue virus non-structural protein 1 (NS1) in blood (serum) during the first 7 days of illness is indicative of a current or recent dengue virus infection. Indications for use of commercial NS1 ELISA tests, and interpretation of positive NS1 ELISA test results may vary. A negative result from a RT-PCR or NS1 ELISA test does not rule out infection. A positive result by RT-PCR or NS1 ELISA meets the confirmatory laboratory criteria for diagnosis in the National Notifiable Diseases Surveillance System (NNDSS) dengue case definition.

Tourniquet Test

Example of positive tourniquet test (right arm).

• Tests for capillary fragility as a sign of Severe Dengue
• Typically used in the absence of available DIC labs (i.e., low-resource settings)
  • Sensitivity of 52% and specificity of 82.4%
  • A positive tourniquet test combined with lekuopenia increases sensitivity to 94%
  • Inflate cuff to pressure between SBP & DBP, and leave for 5 min
  • (+) Test = 10-20 petechiae per square inch

Management

Dengue

• Supportive Care
  • Acetaminophen for pain/fever
    • DO NOT use aspirin or ibuprofen due to increased risk of hemorrhage

Severe Dengue

Above plus:

• Monitor for shock and reduce the risk of complications resulting from increased vascular permeability, plasma leakage, and organ damage.
• IVFs
• Blood Transfusion - consider in hemorrhagic shock

Disposition

Dengue

• Typically outpatient, if well hydrated and non-toxic appearing
• May consider admitting certain high-risk patients (e.g., pregnant, extremes of age, concerning concomitant chronic disease)

Severe Dengue

• Typically admitted
  • Consider ICU admission for patients with shock and end-organ damage

Prevention

• The vaccine Dengvaxia was approved by the Food and Drug Administration in 2021 and was recommended for children and adolescents aged 9 – 16 years who had a laboratory confirmed previous dengue virus infection AND live in areas where dengue is common. However, production of this product was discontinued due to low demand and currently, no vaccines are available..

See Also

• Travel Medicine
• Neglected Tropical Diseases