Dengue Flashcards
Dengue virus characteristics
RNA single stranded virus with four genetically distinct serotypes
Dengue vectors
Aedes agypti and aedes albopictus (day biting)
Dengue clinical features
Fever, myalgia, retro-orbital headache, joint pain
Maculopapular rash
Petechial rash on hands and feet after 4 days
White spots in a sea of red during recovery
Dengue - geographical distribution
South America, Asia, Africa
Dengue warning signs
Severe abdominal pain
Persistent vomiting
Liver enlargement
ALT >1000
Fluid accumulation (plasma leakage)
Lethargy
Sudden drop in platelet count
Rising haematocrit
Narrow pulse pressure
The role of NS1 protein in dengue
- Glycoprotein which stabilises the viral replication system
- Disrupts endothelial dysfunction
- Activation of Toll-like receptor 4 which triggers cascade of complement
Host factors in the severity of dengue
- Children more likely to get plasma leakage
- Adults more like to have bleeding and organ damage
Other at risk characteristics:
- Children
- Pregnant women
- > 60 years
- DM and HTN
Viral factors affecting disease severity in dengue
- High viral load
- High NS1
- Genotype
Antibody dependent enhancement in dengue
More severe dengue in subsequent episodes because:
1. Primary dengue infection - body makes antibodies against that particular serotype
2. Secondary dengue infection - the body partially recognises it, and antibodies bind but are not completely effective at neutralising it
3. The antibodies stick to the virus forming a protective coat, allowing it to get a “free pass” into immune cells
4. As a result there is increased viral replication
Dengue management
Supportive therapy
Careful fluid balance
Often platelet transfusion/antivirals are not helpful
Dengue diagnostics
1st week of illness:
Identification of viral RNA and NS1 Ag using ELISA
End of 1st week:
IgM, IgG
Rapid tests, often combining NS1 detection with Ab test
Challenges in dengue diagnostics
PCR: need centralised lab, expensive, narrow window
NS1: Poor sensitivity (DENV 2)
Cross reactivity with other flaviviruses
Dengue prevention measures
- Vaccination - Dengvaxia - tetravalent live-attenuated and Takeda Q denga.
Challenge in covering multiple serotypes, and cause more severe disease in those who are infection naive. - Vector control - insecticides and avoiding standing water
- Wolbachia program
What are the phases of disease in dengue?
- Febrile phase
- Critical phase
- Recovery phase
What are the criteria for severe disease in dengue?
- Severe haemorrhage
- Severe plasma leakage
- Severe organ involvement (AST/ALT>1000)
