Lecture 18 - Emerging Viral Disease Flashcards Preview

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Flashcards in Lecture 18 - Emerging Viral Disease Deck (49):
1

What is an emerging viral disease?

- Newly appeared

OR

- Previously existed, but rapidly increase in incidence or geographical range

2

What is an emerging viral disease?

- Newly appeared

OR

- Previously existed, but rapidly increase in incidence or geographical range

3

What are some examples of emerging viral disease?

SARS-CoV
HIV
Ebola

4

What are some factors that lead to the emergence of new disease?

- Mutation rate of viruses
- Ecological changes
- Human demographics and behaviour
- Air travel
- Technology and industry
- Public health measures

5

Most emerging viral diseases are...

Zoonoses

6

What are some examples of zoonoses?

Birds: influenza
Monkeys: HIV
Bats: SARS-CoV

7

What does SARS stand for?

Severe acute respiratory syndrome

8

Describe what happened in the SARS epidemic

2003
First cases in China
Spread to 32 countries
800 people died
$20 billion

9

What are the symptoms of SARS?

Fever
Cough
Shortness of breath
Chest X ray --> pneumonia

+ + exposure to SARS patient

10

How was SARS transmitted?

Person - person

11

What are some examples of emerging viral disease?

SARS-CoV
HIV
Ebola

12

What are some factors that lead to the emergence of new disease?

- Mutation rate of viruses
- Ecological changes
- Human demographics and behaviour
- Air travel
- Technology and industry
- Public health measures

13

Most emerging viral diseases are...

Zoonoses

14

What are some examples of zoonoses?

Birds: influenza
Monkeys: HIV
Bats: SARS-CoV

15

What does SARS stand for?

Severe acute respiratory syndrome

16

Describe what happened in the SARS epidemic

2003
First cases in China
Spread to 32 countries
800 people died
$20 billion

17

What are the symptoms of SARS?

Fever
Cough
Shortness of breath
Chest X ray --> pneumonia

+ + exposure to SARS patient

18

How was SARS transmitted?

Person - person
Airbone droplets from sneezing

19

What was interesting about the spread of SARS?

20% of cases were Health Care workers --> defied normal control measures

Superspreaders: some people spread the virus to a huge number of people

20

What type of virus is SARS?

Corona virus

21

What is the natural host of SARS?
What other animal was a host to a similar corona virus?

Bats

Civit cat

22

Which subtypes of influenza are endemic in man?

Type A:
H1N1
H3N2

23

Which cells in man are infected by influenza?
How about in birds?

What is the significance of this?

Humans: Cells bearing SA a2-6 Galactose

Birds: cells bearing SA a2-3 Gal

Normally prevents avian viruses from infecting man

24

What happens when the aviacn virus infects man?

Why?

Pandemic

Because no one has any antibody to the new subtype

25

How is antigenic shift different from antigenic drift?

Describe antigenic shift

Shift:
• bigger change in a shorter period of time
• two different strains / subtypes coming together
• mixture of surface antigens

26

What is the cause of a pandemic?

Antigenic shift

This is when there is suddenly a new subtype that can infect man

27

What were the influenza pandemics seen in the 20th century?

Spanish flu: H1N1
Asian flu: H2N2
Hong Kong flu: H3N2

28

What happens to the existing subtype when there is a pandemic?

The old subtype is replaced.

eg. H3N? --> H1N1 in Spanish flu

29

How do new human subtypes come about?

Antigenic shift
Mechanism:
• Reassorment
• direct invasion with avian strain, then mutation

30

Describe what happened in the Spanish flu pandemic?

25-30% population infected
50 million deaths
15-30 yo mainly affected
During WWI

31

What were the symptoms of Spanish flu?

Pulmonary oedema
Haemorrhage
Cyanosis (purple lips)

32

Why was the H1N1 of the Spanish flu so lethal?

Don't know yet, but sequences are currently being studied by Reverse genetics

33

What is the subtype of Avian influenza?

H5N1 HPAI (Highly pathogenic avian influenza)

34

What happens to birds that are infected with H5N1 HPAI?

Infects systemically and rapidly brings death

35

Does H5N1 infect man?

Yes --> lethal

However, it can not be spread from Human-Human

36

How can HPAI infect systemically?

The cleavage site on HA has mutated

It can now be cut by an enzyme found all over the body

37

What is the potential route for an H5N1 pandemic?

1. Mutation --> Becomes virulent to poultry

2. Infects man directly with low efficiency

3. Antigenic drift, so that it affects man with high effiency

PANDEMIC

38

In 1997, there were 20 cases of Avian flu in man. How was the epidemic halted?

Culling of poultry

39

What is the fatality rate of avian flu?
How does this compare to seasonal epidemic influenza?

H5N1: 60%

Seasonal epidemic influenza: 0.01%

40

Which drugs are effective against avian flu?

NA inhibitors

41

Describe the process of reassortment?

In a 'mixing vessel'
• Pig cells have surface receptors that allow invasion by both human and avian influenza
• Single cell infected with both strains at once
• reassortment
• New strain:
- human internal proteins
- avian HA and NA

42

What does reassortment bring about?

Antigenic shift

43

Describe the origin of the 2009 H1N1 pandemic?

1918 H1N1 in North America
+ Swine viral genes

2009 Pandemic H1N1

44

Describe the infection caused by 2009 H1N1 Swine flu

Same as seasonal influenza:
• fever
• cough
• muscle pains
• malaise
• fatigue

NB not systemic

45

Compare lethality of Swine flu, Avain flu and seasonal influenza

Avian flu is highly lethal

Both Swine flu and seasonal influenza aren't very lethal, unless the individual is immunosuppressed

46

Compare replicative ability of seasonal flu and swine flu

Swine flu has a greater ability to replicate in lungs

Younger people are getting viral pneumonia

47

How is Swine flu treated?

NA inhibitors

48

Can we make vaccines against H5N1 now for when it becomes a pandemic?

Yes, but they probably wouldn't be effective due to antigenic drift

49

How can we treat H5N1 if it becomes a pandemic?

NA inhibitors
However, we won't be able to produce enough