Epidemiology of TB

1. EPIDEMIOLOGY OF
TUBERCULOSIS
Dr. M. Geetha

2. Synopsis
• Introduction
• History of TB- Timeline
• Epidemiological indices
• Geographical distribution in Estimates of TB-
World, SEAR & India
• Time Trends in estimates of TB
• Person distribution of TB
• Agent, Host & Social factors
• Natural history of disease

3. Learning objectives
By the end of this session the students will be
able to
1. Describe the time, place & person
distribution of Tuberculosis
2. Specify the epidemiological determinants of
TB
3. Describe how TB is spread from person to
person
4. Describe the Natural history of TB

4. Introduction
• Infectious disease caused
by Mycobacterium
tuberculosis
• Can also affect intestines,
meninges, bones & joints,
lymph glands, skin and
other tissues
• Also affects animals like
cattle- Bovine
tuberculosis
TB is curable &
preventable

5. History of TB- Timeline
400 B.C.
1500- Giralamo 1860’s- Louis
3700 B.C TB in Hippocrates-
Fracastoro (Italy)- Pasteur- airborne
ancient Egypt excellent clinical
TB contagious transmission
description
1944- 1930’s- William
Streptomycin Wells- conclusive 1882- Robert Koch-
1921- BCG
evidence of Isolation of TB
1952- Isoniazid introduced
airborne bacillus
1960- 2 years tt. transmission
2011/12- atleast 1
1993- Global 2006- I case of
1970’s – MDR TB case of XDR-TB in
health emergency XDR-TB
69 countries

6. Tuberculosis-one of the biggest public
health challenges facing world today
• One of the oldest diseases known
• M. tuberculosis - one of the first bacterial
pathogens identified
• Etiopathogenesis clearly understood
• Vaccine available for close to a century
• Effective treatment available for > 60 years
2nd only to HIV/AIDS as an infectious cause of
death worldwide
Declared Global Public Health Emergency in 1993

7. Epidemiological indices in TB
1. Prevalence of Infection (Tuberculin index)
2. Incidence of Infection (Annual Infection rate)
3. Prevalence of Disease (Case rate)
4. Incidence of New cases
5. Prevalence of “Suspect” cases
6. Case detection rate
7. Prevalence of drug-resistant cases
8. Mortality rate

9. PLACE DISTRIBUTION

10. Estimated TB Incidence rates, 2010
8.8 million incident cases
12 million prevalent cases Source: Global Tuberculosis Control 2011,
1.4 million deaths WHO

11. Global estimates, 2010
Estimates of Prevalence Estimates of Mortality
• 12 million prevalent cases in • 1.4 million deaths
2010 worldwide (20 deaths per 1
• 178 cases per 100000 lakh population)
population • 1.1 million deaths among
HIV negative
• 0.35 million deaths among
HIV positive
Source: Global Tuberculosis Control 2011, WHO

12. TB: A Global Health Crisis
• Nearly 1% of the world’s population newly
infected each year
• Overall 1/3rd of world’s population, nearly 2
billion people are infected with TB
• 200 million people worldwide, or 10% of those
infected will develop active TB & be able to
infect others (10-15 persons per year) for 3
decades
• TB kills 8000 people a day- i.e. 2-3 million people
each year
www.who.int/tbfacts/en

13. 7 billion
1/3rd of world population
2 billion infected
with TB
10% of the infected
people
200 million will
develop active TB

14. 5 million prevalent cases
3.5 million incident cases
5 out of 22 high burden countries

15. Estimates of TB burden WHO-SEAR

16. Estimates of TB burden in India, 2010
(provisional)
accounting for an estimated one quarter (26%) of all TB cases worldwide
Estimates of Number (millions) Rate
burden (per 100,000 pop)
Mortality (excluding HIV) 0.32 (0.21 – 0.47) 26 (17 – 39)
Prevalence (including HIV) 3.1( 2 – 4.6) 256 (161 – 373)
Incidence (including HIV) 2.6 (2.0 – 2.5) 185 (167 – 205)
Incidence (HIV positive) 0.110 (0.075 – 0.160) 9.2 (6.1 – 13)
Source: Global Tuberculosis Control 2011, WHO

17. Magnitude of TB in India
• India ranks first with the largest number of
incident cases (2-2.5 million)
• India has about 2.2 million new cases every year
including about 1 million sputum positive cases.
• Estimated 3.5 million cases are sputum positive.
• 0.5 million people in India die from TB every
year.
• MDR-TB Prevalence among new cases: 2.3%

18. TIME DISTRIBUTION

19. Global trends in estimated rates of TB
Incidence, Prevalence & Mortality
Incidence Prevalence Mortality
HIV Positive
Source: Global Tuberculosis Control 2011

20. Global trends- contd..
• Absolute number of incident TB cases has been
on ↓ since 2006
• 128 incident cases per 100000 population in 2010
• 59% in Asia (26% in Africa)
• 22 High burden countries accounted for 81% of
cases
• Incidence rate falling by 1.3% per year since 2002
• TB mortality decreasing- close to STOP TB
partnership goal
• TB prevalence decreasing, but…

21. Trends in SEAR, 1990-2010
Source: Global Tuberculosis Control 2011

22. Estimated prevalence rate in member
states of SEAR
Source: Global Tuberculosis Control 2011, WHO

23. Estimated mortality rates in member
states of SEAR
Source: Global Tuberculosis Control 2011, WHO

24. TB Trends in India
Source: Global Tuberculosis Control 2011, WHO

25. PERSON DISTRIBUTION

26. Human and Economic Impact
• TB kills more adults than all other infectious diseases
combined.
• More than one-quarter of all avoidable adult deaths
are caused by TB.
• TB strikes people in their most productive years, i.e.
between the ages of 15 to 44.
• Leading killer of people infected with HIV worldwide.

27. Age & sex distribution of all notified new smear
positive cases in WHO-SEAR in 2010

28. TB & Women
• TB is the single biggest killer of young women.
• 3.2 million incident cases among women in
2010 (36%)
• 0.32 million deaths from TB among women in
2010
• Over one million women may needlessly die
from TB this year. They are breadwinners,
mothers, daughters and wives.

29. TB & Children
• In 2010, 0.5 million children (0-14 years) infected
with TB; 64000 child deaths due to TB
• Over 100,000 children may needlessly die from
TB this year.
• Hundreds of thousands of children will become
TB orphans this year.

30. TB & HIV
• 1 in 3 HIV infected people
worldwide co-infected
with TB
• People who are HIV-
positive & infected with
TB are 30 times more
likely to develop active TB
• Among 1.4 million TB
deaths in 2010, 0.35
million deaths were in
HIV positive.

31. AGENT FACTORS- Agent
• My. tuberculosis
• Human strain
responsible → majority
of the cases
ROBERT KOCH (Germany, 1882)

32. Source of Infection
Human source: human Bovine source: infected
case whose sputum is milk
positive for the bacilli

33. Infective material & Communicability
• Infective material is the
sputum of TB patients
• Infective as long as the
persons are untreated
• Effective chemotherapy
reduces infectivity by
90% in 48 hours

34. Host factors
• Age: all ages; sharp ↑ in Risk groups
infection rates from • People who are
childhood to adolescence malnourished
• Sex: Males > Females • People who live in close
• Heredity: not hereditary; quarters
inherited susceptibility is • Healthcare workers
an important risk factor • Long-term hospital
• Nutrition patients
• Immunity: acquired • Prison workers & inmates
(natural infection/ BCG • People with weakened
vaccination) immune systems

36. Latent TB → Active TB: Risk factors
Biomedical Environmental Socioeconomic
• HIV infection • Indoor air • Overcrowding
• Diabetes pollution • Urbanization
• Tobacco • Inadequate • Migration
• Malnutrition ventilation • Poverty
• Silicosis • Population
• Malignancy explosion

37. References
• Park’s Textbook of Preventive and Social
Medicine
• Tuberculosis in South-East Asian Region, 2012,
WHO
• Global Tuberculosis Control, WHO Report
2011
• http://www.who.int/tbfacts/
• http://www.cdc.gov/tb/publications/pamphle
ts/TB_disease_EN_rev.pdf

38. THANK YOU