Mosquito-borne Viruses

Question 1

What type of virus is Dengue?

Answer 1

Flavivirus (+ssRNA) w envelope

Question 2

Where are the antigenic determinants (group, subgroup, type specific) of the Dengue Virus found?

Answer 2

Viral envelope (on the glycoproteins)

Question 3

How many serotypes of Dengue are there?

Answer 3

4

Question 4

What are some members of the Flavivirus family?

Answer 4

Zika, Yellow Fever, West Nile, Dengue

Question 5

What type of vaccine is available for Yellow Fever?

Answer 5

Live attenuated

Question 6

What type of vaccine is available for West Nile Virus?

Answer 6

None

Question 7

What is the most important concern for West Nile Viral infections?

Answer 7

Fatal encephalitis

Question 8

Where and how does West Nile Virus spread?

Answer 8

By Culex mosquitoes mainly in Africa

Question 9

Where and how does Yellow Fever Virus spread?

Answer 9

By Aedes mosquitoes mainly in Africa and Latin America

Question 10

What are the characteristic presentations of Yellow Fever?

Answer 10

Jaundice → yellow
Fever

Question 11

Where and how does Zika Virus spread?

Answer 11

By aedes mosquitoes mainly in Africa

Question 12

What are the 2 most common differential diagnoses for a Dengue infection?

Answer 12

Chikungunya Fever and Zika

Question 13

What are some typical clinical features of Zika infection?

Answer 13

Similar to dengue + conjunctivitis
- microcephaly
- Guillain-Barre syndrome
- Neuropathy (acute sensory polyneuropathy)

Question 14

How is Dengue transmitted?

Answer 14

By Aedes aegypti>albopictus

Question 15

How is Dengue prevented?

Answer 15

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

Question 16

How is dengue diagnosed?

Answer 16

1) Serology
- Haemoglobin Inhibition
- NS1 Ag ELISA
- IgG IgM ELISA
- POCT

2) RT-PCR

3) Viral isolation from live mosquitoes

Question 17

Which anti-virals should you prescribe for a Dengue infection?

Answer 17

None available

Question 18

What is the main reservoir for Dengue?

Answer 18

Humans (but monkey in jungle)

Question 19

What is the pathogenesis of Dengue?

Answer 19

Virus replicates @ infection site and local lymphatics
When internalised, dengue replicated in mononuclear phagocytes where it uses the mobile cells to spread.

Question 20

Can a person get infected by the same serotype twice?

Answer 20

No

Question 21

What are the 3 WHO classifications for Dengue cases?

Answer 21

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)

Question 22

What are the possible outcomes of a Dengue infection?

Answer 22

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

Question 23

What are the 2 lab criteria for DHF?

Answer 23

1) Thrombocytopaenia (<100000/mm^3)
2) Haemoconcentration (hemocrit↑ >20%)

Question 24

How should you manage dengue fever?

Answer 24

Treat symptomatically

Question 25

How should you manage DHF or DSS?

Answer 25

1) Correction of plasma leakage (eg. plasma infusion, plasma expander, electrolyte solution)

2) Symptomatic treatment (eg. paracetamol)
!Avoid Salicylates!

Question 26

What are the 2 groups that can contract DHF/DSS?

Answer 26

DHF → DSS (if untreated)
1) 1st infection (<1y/o)
- protected for maternal IgG until < protective levels → infection-enhancing
- 1st infection of ???