Dengue Fever

General Information

Cause: Dengue Flavivirus (arbovirus), serotypes 1-4

Transmission

Aedes aegypti, Aedes albopictus mosquitoes

• Well adapted to human dwellings
• Estimated that one in twenty homes may contain infected mosquito in endemic areas
• Outbreaks tend to occur early in rainy season

Vertical Transmission

• Mothers infected up to five weeks before delivery can result in acute neonatal dengue
• Fever, cyanosis, apnea, mottling, hepatomegaly, thrombocytopenia

Distribution

• Tropical/subtropical regions, specifically Asia, Africa, Central America, Caribbean
• Most cases occur in Southeast Asia (Indonesia, Myanmar, Sri Lanka, Cambodia, Thailand in particular)
• Mosquitoes cannot live at high altitude, such as the Andes
• There have been increased reports of dengue in US Virgin Islands, Puerto Rico, and US-Mexico border areas

Incidence

• 50-100 million cases of fever worldwide
• Hundreds of thousands of cases of hemorrhagic fever yearly
• Concern for increasing number of cases with global increase in temperature, increased population density, and increased world air travel
• Children are at higher risk of severe infection. Children ages 7-12 are most common age group for hemorrhagic fever and shock.

Definitions to Consider

Dengue: Name of arbovirus

Dengue Fever: Also called “breakbone fever.” Variable presentation depending on age, ranging from mild to severe febrile illness.

Dengue Hemorrhagic Fever: Fever + hemorrhagic manifestations + thrombocytopenia + plasma leakage

Dengue Hemorrhagic Shock: Hemorrhagic fever + hypovolemia/shock + coagulopathy/DIC + severe bleeding

Clinical Manifestations

High Fever

• Often >39°C, lasts 2-7 days
• Often has brief resolution and recurrence

“Breakbone”

• Headache, often frontal or retro-orbital
• Arthralgias and myalgias after onset of fever can be severe and debilitating

GI Symptoms

• Abdominal pain
• Nausea, vomiting, anorexia
• Hepatomegaly
• GI bleeding in hemorrhagic forms

Rash

• Starts as flushed skin
• As fever subsides, macular rash that spares palms and soles may develop
• Rash fades and desquamates, often leaving groups of petechiae on extensor surfaces

Diagnosis

Primarily clinical.

Criteria for Probable Dengue

• Live in or travel to endemic area with fever and two of the following:
  
  *Abdominal pain, fluid overload, mucosal bleed, lethargy, hepatomegaly, increased HCT
• Severe dengue
  • Plasma leakage: shock, respiratory distress
  • Hemorrhage
  • Organ involvement: altered mental status, elevated LFTs

Laboratory Investigation

• Confirmatory studies unlikely to help EM physician
  • Viral culture
  • PCR
  • IgM, IgG seroconversion
• CBC: hemoconcentration from plasma loss, leukopenia is characteristic of disease
• CMP: evaluate LFTs. Hepatitis can be fatal
• Coags, including d-dimer: DIC is complication of severe disease

Imaging

• CXR, US to evaluate for pleural effusion from capillary leakage
• Some studies suggest that gallbladder may be thickened in severe pediatric cases

Differential Diagnosis

*Emerging infectious disease with similar presentation, associated with fever and prolonged arthralgias for up to years.

Management

Dispo is Key Decision in Management

• Patients who are well-hydrated and without warning signs can be sent home
  • Patients should be instructed to return to ED if they develop abdominal pain, signs of bleeding (epistaxis, GI, vaginal), dehydration, SOB, or altered mental status.
• High-risk patients (pregnant, elderly, children, chronic disease) should be admitted
• ICU for patients in shock, evidence of end-organ damage, or requiring transfusion.

Treatment

• No specific medication for dengue, however, good supportive care has substantially decreased mortality
• Acetaminophen
• Do not use aspirin, due to hemorrhagic nature of the disease
• Crystalloid IVF are mainstay of treatment. Slightly above maintenance IVF is ideal once patient has been resuscitated, generally speaking. WHO guidelines offer more comprehensive algorithm.

Treatment Updates

• Adding blood component transfusion to children in hemorrhagic shock may be beneficial, though the stage of illness at administration is still unclear.
• Review of 284 patients with dengue shock treated with corticosteroids showed no improvement in mortality or need for transfusion.
• Small studies and case reports indicate that anti-D immunoglobulin may increase platelet count in thrombocytopenic patients.
• Chloroquine shows no improvement in hospitalized patients.
• Starch preferred to dextran in severe shock in children, though isotonic crystalloids are still preferred to both.

Prevention

• Several vaccines are available, but no vaccine has shown efficacy at this point.
• Geared towards individual/household protection from mosquitoes and environmental elimination.

Advice for Those Traveling to Endemic Regions

• Wear clothing that covers arms and legs, particularly in morning and late afternoon.
• Use insect repellant.
• Choose accommodations with well-screened windows or air conditioning.
• Mosquitoes tend to live indoors and live in cool places (closets, under beds, behind curtains, in bathrooms, in vases).

Further Reading