Lecture 31 - Dengue

Question 0

What are the different types of DENV?

What is important about these types?

Answer 0

DENV-1
DENV-2
DENV-3
DENV-4

Antigenetically cross reactive

Question 1

What sort of infection does DENV cause?

Answer 1

Acute, systemic
- clinically mild

May be asymptomatic

Question 2

How is Dengue transmitted?

Answer 2

Mosquito vector

Aedes aegypti

Question 3

If an individual has been infected with one type of dengue, what can we say about infection in the future?

Answer 3

Same type: lifelong immunity

Different type: enhanced risk of more serious disease

Question 4

What are our treatment and prevention options for Dengue?

Answer 4

No antivirals

No vaccine

Question 5

Which group is most susceptible to infection in endemic countries

Answer 5

Paediatric population commonly affected

Question 6

What is the infectious period ?

Answer 6

4-6 days

Question 7

What are the incubation periods?

Answer 7

Extrinsic: incubation in the mosquito

Intrinsic: time from mosquito bite until clinical manifestations are seen.

Question 8

What are the common symptoms of Dengue infection?

Answer 8

Fever
Headache
Myalgia
Fatigue
Vomiting
Anorexia
Joint pain

Question 9

What is happening in severe dengue?

Answer 9

Severe plasma leakage
Haemorrhage
Organ impairment

‘Dengue shock syndrome’

Question 10

To which countries is Dengue endemic?

Answer 10

South East Asia
India
Central Africa
South America

Question 11

Why is Dengue a new virus?

Answer 11

Urbanisation

Human movement

Question 12

How many cases of Dengue per year?

Answer 12

100 million symptomatic

2.1 severe cases

Question 13

Describe the epidemiology of Dengue in southern Vietnam

Answer 13

Heterogeneous

Differs year to year

• location
• incidence

Question 14

What type of virus is Dengue?

Answer 14

Flavivirus

Question 15

What are some Flaviviruses?

Answer 15

Yellow fever
Japanese encephalitis
West Nile virus

Question 16

Describe the structure of Dengue virus

Answer 16

Envelope
RNA genome
Three structural proteins:
- E
- C
- M

Question 17

What are Dengue genotypes

Answer 17

Named about where they have been genotyped

Multiple genotypes per type eg. DENV-1

Question 18

What is the DENV proteome?

Answer 18

Sequence of all the proteins that this virus makes

Allows us to rationally develop drugs that target these proteins

Question 19

Describe the activity of Aedes aegypti

Answer 19

Lays eggs in artificial containers
Rest on surfac inside homes
Daytime biting of humans
–> mosquito infected for life

Question 20

How are dengue Mosquitos controlled?

Answer 20

Chemical vector control
- no evidence that this works
Education
Vaccine development
Wolbachia introduction into Aedes agypti

Question 21

What is the most developed vaccine in trials?

Answer 21

Live attenuated
Envelope proteins
Tetravalent
In phase III

Phase II results:
- 30% efficacy

Question 22

What is Wolbachia?

Answer 22

Intracellular bacterium
Found in 80% of insects worldwide

Change reproductive behaviour of the mosquitoes that they live in
–> reproductive advantage for Wolbachia infected mosquitoes

Shortens life span of mosquito

Question 23

Why would Wolbachia be introduced into Aedes aegypti ?

Answer 23

The infected mosquitoes will haves shorter life span (10 days shorter)

Reduced likelyhood of transmission of dengue virus

Question 24

What was the result of Wolbachia infection?

Answer 24

Shorter life span

Mosquitoes are resistant to Dengue infection
–> due to competition between Dengue and Wolbachia

Question 25

What are the different Wolbachia strains?

Answer 25

wMel

• fit
• intermediate ability to block dengue virus replication

wMel Pop
- unfit in the field

Question 26

Describe the Yorkeys Knob field trial

Answer 26

After release in 2011, there was an increase in Wolbachia infected Aedes Agypti

Question 27

Describe the intentions of the Pilot field release

Answer 27

• determine if wMelPop is sustainable
• best way of release
• effects on viral interference

Question 28

Describe the results of the Vietnam field trial

Answer 28

So far, increase in percentage of Mosquitoes with Wolbachia