This document discusses the epidemiology of tuberculosis (TB). It defines epidemiology and TB, describes how TB spreads from person to person through airborne droplets. It discusses factors that influence transmission risk and stopping transmission. It also outlines the incubation period, history of TB discoveries, common epidemiological indices used to measure the TB problem, definitions of different TB cases, the natural history of TB including agent and host factors, and the global and national burden of TB, particularly in India which accounts for over 1/5 of global TB incidence.

1. KARAGANDA STATE MEDICALKARAGANDA STATE MEDICAL
UNIVERSITYUNIVERSITY
SUBJECT-EPIDEMIOLOGYSUBJECT-EPIDEMIOLOGY
SIWTSIWT
SUBMITTED TO: AISULUKAMAROVA
SUBMITTED BY: MANOJ
KUMAR
OM PRAKASH
GROUP- 3009

2. EPIDEMIOLOGYEPIDEMIOLOGY OFOF
TUBERCULOSISTUBERCULOSIS

3. EPIDEMIOLOGY
“The study of the distribution and
determinants of health-related states or
events in specified populations, and the
application of this study to the control of
health problems”
TUBERCULOSIS
Tuberculosis is a specific infectious
disease caused by M. tuberculosis. The
disease primarily affects lungs and causes
pulmonary tuberculosis.

4.  TB is spread person to person
through the air via droplet
nuclei
 M. tuberculosis may be
expelled when an infectious
person:
◦ Coughs
◦ Sneezes
◦ Speaks
◦ Sings
 Transmission occurs when
another person inhales droplet
nuclei
TB TRANSMISSIONTB TRANSMISSION

5. TB TRANSMISSIONTB TRANSMISSION
Transmission is defined as the spread of an
organism, such as M. tuberculosis, from one
person to another.

6. Probability that TB will be transmitted depends
on:
Infectiousness of person with TB disease
Environment in which exposure occurred
Length of exposure
Virulence (strength) of the tubercle bacilli
The best way to stop transmission is to:
Isolate infectious persons
Provide effective treatment to infectious
persons as soon as possible

7. INCUBATION PERIODINCUBATION PERIOD
The time from receipt of infection
to the development of a +ve
tuberculin test ranges from 3-6
weeks
Incubation period may be week,
month or year

8. Until mid-1800s, many
believed TB was
hereditary
1865 Jean Antoine-
Villemin proved TB
was contagious
1882 Robert Koch
discovered M.
tuberculosis, the
bacterium that causes
TB
HISTORY OF TBHISTORY OF TB
Mycobacterium tuberculosis
Image credit: Janice Haney Carr

9. 1840 19201860 1900 1940 1960 1980 20001880
1993: TB cases decline1993: TB cases decline
due to increased fundingdue to increased funding
and enhanced TB controland enhanced TB control
effortsefforts
1884:1884:
First TBFirst TB
sanatoriumsanatorium
establishedestablished
in U.S.in U.S.
1865:1865:
Jean-Jean-
AntoineAntoine
VilleminVillemin
proved TB isproved TB is
contagiouscontagious
1943:1943:
StreptomycinStreptomycin
(SM) a drug used(SM) a drug used
to treat TB isto treat TB is
discovereddiscovered
1882:1882:
Robert Koch discoversRobert Koch discovers
M. tuberculosisM. tuberculosis
Mid-1980s:Mid-1980s:
Unexpected rise inUnexpected rise in
TB casesTB cases
1943-1952:1943-1952:
Two more drugs areTwo more drugs are
discovered to treatdiscovered to treat
TB: INH and PASTB: INH and PAS
TB HISTORY TIMELINETB HISTORY TIMELINE

10. EPIDEMIOLOGICAL INDICESEPIDEMIOLOGICAL INDICES
Indices or parameters are needed to
measure the tuberculosis problem in a
community
For planning and evaluation of control
measures
Indices are also required for
international comparison

11.  Following epidemiological indices are
generally used in TB :
a) Prevalence of infection:-
 It is the percentage of individual who show a
positive reaction to the standard tuberculin
test.
b) Incidence of infection (Annual infection rate):-
 It is the percentage of population under study
who will be newly infected by M. tuberculosis.
 It reflects the annual risk of being infected in a
given community.

12. c) Prevalence of disease (Case rate) :-
 It is the percentage of individuals who’s
sputum is positive for tubercle bacilli on
microscopic examination.
 It is the best available practical index to
estimate the number of infectious cases
or case load in a community.
d) Indices of new cases :-
 It is the percentage of new tuberculosis
cases per 1000 population occurring
during one year.

13. e) Prevalence of suspect cases :-
 It is based on X- Ray examination of chest.
 Drawback of this index is that radiography
cannot reveal with any certainty.
 That’s why it has no epidemiological
significance.
f) Case detection rate :-
no. of new and relapse cases in a year
estimated incidence of such cases in same year

14. g) Prevalence of new drug resistance
cases :-
 The patients resistance to anti-
tuberculosis drugs.
 Mortality rate :-
 The no. of deaths from TB per lakh
population was used as the index of
the TB problem in a community.
 At present time it has no significance.

15. SOME DEFINATIONS OF TB CASESSOME DEFINATIONS OF TB CASES
NEW CASES – A patient with sputum +ve
PTB who has never treated for TB or
has taken anti- tuberculosis drug for
less than 4 week.
RELAPSE – A patient who return smear
+ve having previously been treated for
TB and cured.
Return after default- A patient who return
sputum smear +ve after having left
treatment for at least 2 months.

16. TRANSFER IN- A patient recorded in another
administrative area register and transferred
into another area to continue treatment.
TRANSFER OUT- A patient who has been
transfer to another area registered and
treatment result are not known.
CURED– Initially smear +ve positive patient
who completed treatment and had –ve smear
result on at least two occasions.
COHORT- A group of patients in whom TB
has been diagnosed and who were registered
for treatment during a specified time period.

17. NATURAL HISTORY OF TBNATURAL HISTORY OF TB
AGENT FACTORS
AGENT
M. TUBERCULOSIS
IS A FACULTATIVE
INTRACELLULAR
PARASITE
SOURCE OF
INFECTION
(TWO SOURCES)
COMMUNICABILITY
PATIENTS ARE REMAIN
INFECTIVE AS LONG
AS THEY REMAIN
UNTREATED
HUMAN SOURCE
MOST COMMON
SOURCE
BOVINE SOURCE
INFECTION USUALLY
BY INFECTED MILK

18. HOST FACTORS
AGE- TB AFFECTS ALL THE AGES
SEX- MORE PREVALENT IN MALES
HERIDITY- TB IS NOT A HERIDITARY
DISEASE
NUTRIENT- MALNUTRITION IS WIDELY
PREDISPOSE TO TB
IMMUNITY- MAN HAS NO INHERITED
IMMUNITY AGAINST TB

19. SOCIAL FACTORS
POOR QUALITY OF LIFE
POOR HOUSING
OVERCROWDING
POPULATION EXPLOSION
UNDERNUTRITION
LACK OF EDUCATION
LARGE FAMILIES
EARLY MARRIAGES etc.

20. GLOBAL BURDEN OF TBGLOBAL BURDEN OF TB
2 billion infected, i.e. 1 in 3 of global population
9.4 million (139/lakh) new cases in 2008, 80% in
22 high-burden countries
About 5.7 million cases were notified through
DOTS programme during 2010
Global incidence of TB has peaked in 2004 and is
declining
1.77 million deaths in 2007, 98% in low-income
countries
1.4 million deaths in 2010
MDR-TB -prevalence in new cases around 3.6%

21. GLOBAL SITUATIONGLOBAL SITUATION
Since 1995, over 21 million patients have
been diagnosed and treated in DOTS
programmes.
In 2007, 5.5 million new and relapse TB
cases were initiated on treatment under
DOTS strategy.
Of 2.5 million new smear positive patients
registered in 2006, 85% were successfully
treated under DOTS.

22. TUBERCULOSIS IN INDIATUBERCULOSIS IN INDIA
 Estimated incidence
1.96 million new cases annually
0.8 million new smear positive cases annually
75 new smear positive PTB cases/lakh population per
year
 Estimated prevalence of TB disease
3.8 million bacillary cases in 2000
1.7 million new smear positive cases in 2000
 Estimated mortality
330,000 deaths due to TB each year
Over 1000 deaths a day
2 deaths every 3 minutes

23. Prevalence of TB infection
40% (~400 million) infected with M.
tuberculosis (with a 10% lifetime risk of TB
disease in the absence of HIV)
Estimated Multi-drug resistant TB
< 3% in new cases
12% in re-treatment cases
TB-HIV
~2.31 million people living with HIV
(PLWHA)
10-15% annual risk (60% lifetime risk) of
developing active TB disease in PLWHA
About 80% of TB patients are between 15-54
year of age, while two- third of the cases are
male.

24. India is the highest TB burden country accountingIndia is the highest TB burden country accounting
for more than one-fifth of the global incidencefor more than one-fifth of the global incidence
Indonesia
6%
Nigeria
5%
Other countries
20%
Other 13 HBCs
16% China
14%
South Africa
5%
Bangladesh
4%
Ethiopia
3%
Pakistan
3%
Phillipines
3%
India
21%
Source: WHO Geneva; WHO Report 2009: Global Tuberculosis Control; Surveillance, Planning and Financing
Global annual incidence = 9.4 million
India annual incidence = 1.96 million
India is 17th
among 22
High Burden
Countries (in terms of
TB incidence rate)

25. REFRENCESREFRENCES
Internet and Wikipedia
K. Park
Vivek Jain