Dengue Flashcards
How many serotypes of dengue are there?
5
DENV-1 to DENV-4 which co-circulate
Putative DENV-5 discovered in 2013 in Malaysia which transmits via sylvatic cycle
Describe immunity relating to infection with a specific dengue serotype
Short term cross reactivity immunity lasts 2-6 months from primary infection, lifelong immunity to infecting serotype
What is the reservoir of dengue?
Humans!
Rare spill over events from sylvatic strains
Which patients are most at risk of severe dengue?
Those with comorbidities
Children
Elderly
Infants with waning passive Ab from mum
Risks of dengue in pregnancy
Preterm/low birth weight
Severe dengue in mum can lead to neonatal death
Vertical transmission can occur
No congenital disease
What are the three phases of dengue? Main aspects and when do they occur?
- Febrile - days 2-7
Fever, myalgia, rash, nausea and vomiting, mild haemorrhagic features, leucopaenia
- Critical - days 3-7 (lasts 24-48 h).
Temp drops below 37C. Increase in haematocrit, leucopaenia, drop in platelets (due to plasma leakage)
Can cause pleural effusion, ascites, organ dysfunction, metabolic acidosis, DIC, hepatitis, encephalitis, severe bleeding and shock
- Recovery - 48-72 h
Gradual re absorption of extra cellular fluids
What is the peak enhancement titre theory in dengue?
Antibody dependent enhancement - when heterotrophic abs bind but do no neutralise virus leading to severe dengue
When there is enough of these heterotrophic abs then they do neutralise, but if not enough then they cause ADE. Backed up by protection from all serotypes 2-6 months after primary infection, and severe dengue in 6-12 months old who have waning maternal Ab
When is the viraemic phase in dengue?
Two days before until 5 days after fever.
Gold standard diagnostic test for dengue? And why?
PRNT
Because viremia is short and IgMs cross react with other flavis, or possibly absent in secondary infection.
