Lecture 27 - TB Epidemiology Flashcards

1
Q

Proportion of global population with latent TB

A

~1/3 (~2 billion people)

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2
Q

Number of cases of TB disease in 2012

A

8.6 million

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3
Q

Number of TB deaths globally in 2012

A

1.3 million

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4
Q

TB incidence in Australia

A

7/100,000 people

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5
Q

TB incidence in Kwa Zulu Natal

A

900/100,000 people

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6
Q

Major recent factor in TB infections

A

HIV pandemic

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7
Q

Incidence

A

New cases in a year

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8
Q

Prevalence

A

All cases in a year

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9
Q

What effect does TB treatment have on TB prevalence?

A

Decrease in prevalence, as treatment decreases amount of time that someone has active TB for

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10
Q

Effect of HIV infection on TB risk

A

Increases risk

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11
Q

Why is the TB rate in Bangladesh stable?

A

Relatively low HIV rate

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12
Q

HIV and TB rates in Brazil

A

Both are decreasing

Introduction of ART correlates with decrease in HIV. Decrease in TB follows decrease in HIV

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13
Q

HIV and TB rates in South Africa

A

HIV rate increases

TB rate increases shortly after HIV increase

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14
Q

Proportion of global TB cases in South-East Asia

A

~55%

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15
Q

Largest risk factor in Australia for TB

A

Being born overseas in a TB high-risk country

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16
Q

Risk of infection over time in a person born in a high-risk TB country, who has moved to Australia
1)
2)
3)

A

1) Greatest risk shortly after arriving Australia
2) Incidence decreases, but still is significant 30 years after arriving in Australia
3) Cumulative risk from immigrants from sub-Saharan Africa, South-East Asia reaches 2.5% after 30 years in Australia

17
Q

Contact tracing

A

If someone has active TB, test their contacts

18
Q

Mean time from exposure of notification of TB infection

19
Q

Multi-drug resistant TB

A

Resistant to isoniazid and rifamycin

20
Q
How to distinguish between TB strains
1)
2)
3)
4)
A

1) Drug resistance
2) Spoligotyping
3) Variable number of tandem repeats (mirutyping)
4) Whole-genome sequencing

21
Q

Highest-resolution technique to distinguish between TB strains

A

Whole-genome sequencing

22
Q

What is spoligotyping?

A

Compare mutatable parts of different TB genomes

23
Q

What is variable number of tandem repeats?

A

Compare parts of TB genomes that have tandem repeats. Compare number. Often compare 24 parts of genome.

24
Q

Beijing strain
1)
2)
3)

A

1) Common TB strain in SE Asia
2) Only 3-4 different variable number of tandem repeat types circulating
3) Hard to distinguish between strains with VNTR. Have to use whole-genome sequencing

25
Demographic versus personal risk of TB 1) 2)
1) Similar baseline level of personal risk of household contact between Australia, South Africa and Peru slums 2) Extra risk based on prevalence of TB in country
26
Case of TB outbreak in British Columbia 1) 2) 3)
1) Contact tracing of active TB initially identified a baby as the index case 2) This was incorrect, as babies are poor transmitters of TB 3) Original epidemiology done with VNTR of 24 loci. Whole-genome sequencing was used, 2 different TB strains were identified
27
Why would a 100% vaccine given to 100% of the population not eliminate TB?
There are still cases of latent TB that can progress to active TB