Mosquito-borne Viruses Flashcards
What type of virus is Dengue?
Flavivirus (+ssRNA) w envelope
Where are the antigenic determinants (group, subgroup, type specific) of the Dengue Virus found?
Viral envelope (on the glycoproteins)
How many serotypes of Dengue are there?
4
What are some members of the Flavivirus family?
Zika, Yellow Fever, West Nile, Dengue
What type of vaccine is available for Yellow Fever?
Live attenuated
What type of vaccine is available for West Nile Virus?
None
What is the most important concern for West Nile Viral infections?
Fatal encephalitis
Where and how does West Nile Virus spread?
By Culex mosquitoes mainly in Africa
Where and how does Yellow Fever Virus spread?
By Aedes mosquitoes mainly in Africa and Latin America
What are the characteristic presentations of Yellow Fever?
Jaundice → yellow
Fever
Where and how does Zika Virus spread?
By aedes mosquitoes mainly in Africa
What are the 2 most common differential diagnoses for a Dengue infection?
Chikungunya Fever and Zika
What are some typical clinical features of Zika infection?
Similar to dengue + conjunctivitis
- microcephaly
- Guillain-Barre syndrome
- Neuropathy (acute sensory polyneuropathy)
How is Dengue transmitted?
By Aedes aegypti>albopictus
How is Dengue prevented?
1) Live attenuated vaccine: Dengvaxia
ONLY for px w previous infection (to prevent immune enhancement)
2) Vector (mosquito) control
i) Source reduction
ii) Adulticide
iii) Health education
iv) Law enforcement
v) Wolbachia field trials
How is dengue diagnosed?
1) Serology
- Haemoglobin Inhibition
- NS1 Ag ELISA
- IgG IgM ELISA
- POCT
2) RT-PCR
3) Viral isolation from live mosquitoes
Which anti-virals should you prescribe for a Dengue infection?
None available
What is the main reservoir for Dengue?
Humans (but monkey in jungle)
What is the pathogenesis of Dengue?
Virus replicates @ infection site and local lymphatics
When internalised, dengue replicated in mononuclear phagocytes where it uses the mobile cells to spread.
Can a person get infected by the same serotype twice?
No
What are the 3 WHO classifications for Dengue cases?
1) Dengue w/o warning sign (non-severe)
2) Dengue w warning signs (deterioration → need strict observation
3) Severe dengue (DSS, sever bleeding, severe organ involvement)
What are the possible outcomes of a Dengue infection?
1) Asymptomatic
2) Dengue fever
- fever
- severe headache, pain behind eyes
- muscle and joint pain
- rash
3) Dengue haemorrhagic fever
- fever
- skin presentations of haemorhage (eg. petechiae, gum bleeding)
-hepatomegaly
4) Dengue shock syndrome (aft. ↓temp)
- hypotension, narrowing pulse pressure
- death 12-24hrs
What are the 2 lab criteria for DHF?
1) Thrombocytopaenia (<100000/mm^3)
2) Haemoconcentration (hemocrit↑ >20%)
How should you manage dengue fever?
Treat symptomatically
How should you manage DHF or DSS?
1) Correction of plasma leakage (eg. plasma infusion, plasma expander, electrolyte solution)
2) Symptomatic treatment (eg. paracetamol)
!Avoid Salicylates!
What are the 2 groups that can contract DHF/DSS?
DHF → DSS (if untreated)
1) 1st infection (<1y/o)
- protected for maternal IgG until < protective levels → infection-enhancing
- 1st infection of ???
