Self-Study Modules 

on Tuberculosis 

Epidemiology
 

of Tuberculosis
 

Module 2: Objectives
 

At completion of this module, learners will be able to: 

1.	 Describe how the number of TB cases reported in 

the U.S has changed over the last 60 years 

2.	 List 5 factors that contributed to the increase of TB 

cases between 1985 and 1992 

3.	 List 3 improvements TB programs made with 

increased funds that have contributed to a 

decrease in TB cases since 1993 

4.	 List groups of people who are more likely to be 

exposed to or infected with M. tuberculosis 

5.	 List groups of people who are more likely to 

develop TB disease once infected with M. 

tuberculosis Module 2 – Epidemiology of Tuberculosis 

Module 2: Overview 

•	 Introduction to TB Epidemiology 

•	 People at High Risk for TB Infection and TB 

Disease 

•	 Case Studies 

Module 2 – Epidemiology of Tuberculosis 3 

Introduction to TB
 

Epidemiology
 

Epidemiology (1) 

Epidemiology is the study of the distribution 

and causes of disease and other health 

problems in groups of people. 

Module 2 – Epidemiology of Tuberculosis 5 

Epidemiology (2) 

•	 Epidemiologists: 

– Determine frequency and pattern of health 

problems in communities 

– Try to figure out why health problems are 

occurring 

Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

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2 

4 

6 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Global Epidemiology of TB 

•	 TB is one of the leading causes of death due 

to infectious disease in the world 

•	 Almost 2 billion people are infected with M. 

tuberculosis 

•	 Each year about: 

– 9 million people develop TB disease 

– 1.5 million people die of TB 

Module 2 – Epidemiology of Tuberculosis 7 

TB Reporting in U.S. 

•	 The Report of Verified Case of Tuberculosis 

(RVCT) is the national TB surveillance data 

collection form and is used for reporting all 

verified TB cases to CDC 

–	 The 50 states, District of Columbia, New 

York City, Puerto Rico, and 7 other 

jurisdictions in the Pacific and Caribbean 

report TB cases to CDC 

•	 Health care providers are required by law to 

report TB cases to state or local health 

departments 

Module 2 – Epidemiology of Tuberculosis 

U.S. Epidemiology of TB	 

1953 - 1986 

•	 1953: 

– More than 84,000 cases of TB 

• 1953-1984: 

– TB cases declined about 6% each year 

• 1985: 

– TB cases reached a low of 22,201 

• 1986: 

– Significant increase in TB cases began 

Module 2 – Epidemiology of Tuberculosis	 

U.S. TB Resurgence (1) 

1986 - 1992 

 

30,000 

25,000 

No. of Cases 

20,000 

15,000 

10,000 

5,000 

0 

Reported TB Cases, U.S., 1982-2014 

9	 Module 2 – Epidemiology of Tuberculosis 10 

U.S. TB Resurgence (2) 

1986 - 1992 

•	 Contributing factors: 

– Inadequate funding for TB control and other public 

health efforts 

– HIV epidemic 

– Increased immigration from countries where TB is 

common 

– Spread of TB in certain settings (e.g., homeless
 

shelters and correctional facilities)
 

– Spread of multidrug-resistant TB (MDR TB) 

Module 2 – Epidemiology of Tuberculosis 11 

U.S. TB Control and Prevention (1) 

1993 - 2014 

•	 1993-2014: 

– Number of TB cases reported annually in U.S.
 

steadily declined
 

•	 Increased federal funds and other resources allowed 

TB programs to improve control efforts to: 

– Promptly identify persons with TB 

– Start appropriate initial treatment for TB cases 

– Ensure patients complete treatment 

– Conduct contact investigations Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

2
 

8 

12 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

U.S. TB Control and Prevention (2)	 

1993 - 2014 

 

0 

No. of Cases 

30,000 

25,000 

20,000 

15,000 

10,000 

5,000 

Reported TB Cases, U.S., 1982-2013 

Module 2 – Epidemiology of Tuberculosis 

Continuing Challenges in TB 

Control 

13 

•	 TB is reported in almost every state and is 

increasing in some areas 

•	 More than half of all TB cases in the U.S. are 

among foreign-born persons 

•	 TB affects racial/ethnic minorities 

disproportionately 

•	 MDR TB and extensively drug-resistant TB (XDR 

TB) remain serious public health concerns Module 2 – Epidemiology of Tuberculosis 

TB Case Rates (1) 

•	 A case rate is the number of TB cases that 

occur during a certain time period, divided 

by size of the population at that time 

•	 Often expressed in terms of a population size 

of 100,000 persons 

Module 2 – Epidemiology of Tuberculosis 15 

TB Case Rates (2) 

Example: 

•	 In the U.S. in 2014, there were 9,421 new TB 

cases in a population size of 318,857,056 

9,421 x 100,000 = 2.96 

318,857,056 

•	 In 2014, the U.S. TB case rate was 2.96 TB 

cases per 100,000 persons (rounded to 3.0) 

Module 2 – Epidemiology of Tuberculosis 

TB Case Rates by State, 2014
 

 

 

D.C. 

< 3.0* (2014 national average) 

*Cases per 100,000 

Module 2 – Epidemiology of Tuberculosis 17 

TB Case Rates (3) 

•	 Health departments, CDC, and others can 

compare the occurrence of TB in different 

places, time periods, and groups of people 

using case rates 

•	 Comparisons have shown that rates of TB 

are higher in certain groups than in others 

Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

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14 

16 

18 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Epidemiology of TB 

Study Question 2.1 

What happened to the number of TB ca ses in 

the United States between 1953 and 1984? 

Module 2 – Epidemiology of Tuberculosis 

Epidemiology of TB 

Study Question 2.2 

What happened to the number of TB ca ses in 

the United States between 1985 and 1992? 

19 Module 2 – Epidemiology of Tuberculosis 

Epidemiology of TB 

Study Question 2.3 

Name 5 factors that may have contributed to 

the increase in the number of TB cases 

between 1985 and 1992. 

Module 2 – Epidemiology of Tuberculosis 

Epidemiology of TB 

Study Question 2.4 

What happened to the number of TB cases in 

the United States from 1993 to 2014? 

Module 2 – Epidemiology of Tuberculosis 

Epidemiology of TB 

Study Question 2.5 

Name 3 improvements TB programs were 

able to make with increased federal, state, 

and other funds that contributed to the 

decrease in TB cases since 1993. 

21 

Module 2 – Epidemiology of Tuberculosis 

Race and Ethnicity (1) 

•	 TB affects certain racial and ethnic minorities 

disproportionately 

•	 In 2014, about 85% of TB cases in the U.S. 

were among racial and ethnic minorities 

•	 Percentage of TB cases in racial and ethnic 

minorities is higher than expected based on 

percentage of these minorities in the U.S. 

population 

23 Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

4
 

20

22 

24 
Race and Ethnicity (2) 

 

 

 

 

 

 

White Multiple Race 2% 

Black or African 

American 13% 

American Indian or
 

Alaska Native
 

1%
 

Native Hawaiian or 21%
 Other Pacific 


Islander
 

1%
 

Hispanic or Latino 

29% 

Asian 

32% 

Reported TB cases by race and ethnicity, U.S, 2014* 

*All races are non-Hispanic. Multiple Race indicates two or more races reported for a person. 

Does not include persons of Hispanic or Latino origin. 

Module 2 – Epidemiology of Tuberculosis 

Race and Ethnicity (3) 

 

 

 

 

 

 

American Indian or
 

Two or More Races
 Alaska Native 

1% Native Hawaiian or 

Other Pacific Asian 

2% 

Black or African
 

American
 

12%
 

Hispanic or Latino 

17% White 

63% 

5% Islander 0.2% 

Racial and ethnic groups by percentage of U.S. population, 2014 

 

 

 

 

 

 

 

 

 

 

 

 

 

Module 2 – Epidemiology of Tuberculosis 

Race and Ethnicity (4) 

•	 Disparities may exist due to racial and ethnic 

minorities having other risk factors for TB, 

such as: 

– Birth in a country where TB is common 

– HIV infection 

– Low socioeconomic status 

– Exposure to TB in high-risk settings 

Module 2 – Epidemiology of Tuberculosis 

Relative Risk for TB (1) 

Relative risk is a comparison of case rates 

between two groups. 

Module 2 – Epidemiology of Tuberculosis 

Relative Risk for TB (2) 

Example: 

• The case rate for Asians is 17.8 compared to 

0.6 for non-Hispanic whites. Therefore, the
 

relative risk for Asians is about 29 times
 

higher than non-Hispanic whites
 

17.8 (TB case rate for Asians) = 29.6 

0.6 (TB case rate for non-Hispanic whites) 

Module 2 – Epidemiology of Tuberculosis 

Relative Risk for TB (3)
 

Race and Ethnicity, 2014
 

Race/Ethnicity TB Case Rate Relative Risk 

Asians 17.8 29.6 

Native Hawaiians or 

Other Pacific Islanders 16.9 28.1 

Blacks or African 

Americans 5.1 8.5 

American Indians or 

Alaska Natives 5.0 8.3 

Hispanics or Latinos 5.0 8.3 

Multiple Race 2.8 4.6 

Non- Hispanic Whites 0.6 1 

25 

27 

29 Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

5
 

26 

28 

30 
 

 

Race and Ethnicity 

Study Question 2.6 

Which racial and ethnic groups are 

disproportionally affected by TB? 

Module 2 – Epidemiology of Tuberculosis 

People at High Risk for TB


Infection and TB Disease
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

31 

High-Risk Groups 

•	 High-risk groups can be divided into two 

categories: 

– High risk for exposure to or infection with M. 

tuberculosis 

– High risk for developing TB disease after 

infection with M. tuberculosis 

Module 2 – Epidemiology of Tuberculosis 33 

People at High Risk for Exposure to 

or Infection with M. tuberculosis 

•	 Contacts 

•	 People who have come to the 

U.S. within the last 5 years 

from areas of the world 

where TB is common	 

•	 Persons who visit areas with 

a high prevalence of TB 

disease 

•	 People who live or work in 

high-risk congregate settings 

•	 Health care workers who 

serve patients at increased 

risk 

• Populations defined 

locally as having an 

increased incidence of 

LTBI or TB disease,
 

possibly medically
 

underserved, low-income 

populations, or persons 

who abuse drugs or 

alcohol 

•	 Infants, children, and 

adolescents exposed to 

adults who are at 

increased risk for LTBI or 

TB disease 

Module 2 – Epidemiology of Tuberculosis 

People at High Risk for Developing 

TB Disease after Infection with M. tuberculosis (1) 

•	 People living with HIV 

•	 Children younger than 5 years of age 

•	 People infected with M. tuberculosis within past 2 years 

•	 People with a history of untreated or inadequately
 

treated TB disease
 

•	 People who are receiving immunosuppressive therapy 

•	 People with silicosis, diabetes mellitus, chronic renal
 

failure, leukemia, or cancer of the head, neck, or lung
 

Module 2 – Epidemiology of Tuberculosis 35 

People at High Risk for Developing 

TB Disease after Infection with M. tuberculosis (2) 

•	 Persons who have had a gastrectomy or jejunoileal 

bypass 

•	 Low body weight 

•	 Cigarette smokers and persons who abuse drugs or 

alcohol 

•	 Populations defined locally as having an increased 

risk 

Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

6
 

32 

34 

36 
 

 

 

 

 

 

 

 

 

 

 

 

High-Risk Groups for TB Infection (1)
 

Contacts 

•	 Contacts are persons 

who have spent time 

with someone who has 

infectious TB disease 

• May include: 

– Family members 

– Coworkers 

– Friends 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (2) 

Foreign-Born Persons/Immigrants 

Other
 

Countries Philippines 

38% 

Mexico 

(21%) 

India 

(8%) 

Guatemala Vietnam 

(8%) 

China 

(7%) (3%) 

Haiti 

(3%)	 

(12%) 

In the U.S., LTBI
 

and TB disease
 

often occur among
 

people born in
 

areas of the world
 

where TB is 

common: 

– Asia 

– Africa 

– Russia 

– Eastern Europe 

– Latin America 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (3)

Foreign-Born Persons/Immigrants
 

 

 

U.S.-born

73%

U.S.-born

35%

-

- Foreign-born 

27% 

Foreign-born 

65% 

U.S. born 

73% 

Foreign-born 

27% U.S. born 

34% 

Foreign-born 

66% 

1992 2014
 

Cases of TB in foreign-born and U.S.-born,
 

1992 and 2014
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (4) 

Foreign-Born Persons/Immigrants 

•	 To address high rates of TB in foreign-born
 

persons, CDC and other public health
 

organizations are working to:
 

– Improve the overseas and domestic screening 

process for immigrants and refugees 

– Strengthen the notification system that alerts 

health departments about the arrival of immigrants 

and refugees with suspected TB disease 

– Test recent arrivals from countries where TB is 

common for TB infection and ensure completion of 

treatment 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (5)

Foreign-Born Persons/Immigrants 

•	 Individuals applying for immigration and
 

refugee status from overseas:
 

– Must be screened for TB by panel physicians 

before entering the U.S. 

– Must have completed treatment before
 

entering the U.S. if diagnosed with TB
 

disease
 

Module 2 – Epidemiology of Tuberculosis 41 

37 


 

39 

High-Risk Groups for TB Infection (6) 

Foreign-Born Persons/Immigrants 

•	 Immigrants living in the U.S. who apply for
 

permanent residence or citizenship:
 

– Must be tested for TB infection and evaluated 

for TB disease by U.S.- based civil surgeons 

Module 2 – Epidemiology of Tuberculosis 42 

Module 2 - Epidemiology of Tuberculosis
 

7
 

38 

40 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

High-Risk Groups for TB Infection (7)
 

Congregate Settings 

•	 In certain congregate settings, the risk of 

being exposed to TB is higher than other 

places. This may include: 

– Correctional facilities 

– Homeless shelters 

– Nursing homes 

– Health care facilities 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (8)
 

Congregate Settings 

•	 Risk of exposure to TB is higher than in other 

settings 

•	 Risk is higher if facility is crowded 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (9) 

Correctional Facilities 

•	 Higher risk in correctional facilities may be due 

to: 

– Incarcerated population includes a high proportion 

of people at greater risk for TB than overall 

population (risk factors may include HIV-infection 

and a history of homelessness or drug use) 

– Physical structure of correctional facilities (e.g., 

close living quarters, overcrowding, potential for 

inadequate ventilation) 

– Movement of inmates into and out of facilities can 

lead to interruption of therapy 

Module 2 – Epidemiology of Tuberculosis 45 

High-Risk Groups for TB Infection (10) 

Health Care Workers 

•	 Might be exposed to 

TB at work 

•	 Risk depends on: 

– Number of persons
 

with TB in facility
 

– Job duties 

– Infection control
 

procedures
 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (11) 

Populations Defined Locally 

Populations that may have 

an increased risk include 

•	 Persons experiencing 

homelssness 

•	 Medically underserved 

populations 

•	 Low-income groups 

•	 Persons who abuse drugs 

or alcohol 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection (12) 

Populations Defined Locally 

•	 Low-income is linked to higher risk of TB 

exposure 

•	 Possible reasons include factors associated with 

low-income: 

– Inadequate living conditions 

– Crowding 

– Malnutrition 

– Poor access to health care 

•	 TB rates are 10 times higher for people 

experiencing homelessness 

Module 2 – Epidemiology of Tuberculosis 

43 

47 

Module 2 - Epidemiology of Tuberculosis
 

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44 

46 

48 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

High-Risk Groups for TB Infection (13)
 

Children and Adolescents 

•	 High risk if exposed to adults 

in high-risk groups 

•	 If a child has TB infection or 

disease, it suggests that: 

– TB was transmitted
 

relatively recently
 

– Person who transmitted TB 

to child may still be 

infectious 

– Others may have been 

exposed Module 2 – Epidemiology of Tuberculosis 49 

High-Risk Groups for TB Disease (1) 

Infants and Children Younger than 5 Years 

High risk for rapidly developing TB disease due to 

underdeveloped immune system 

Module 2 – Epidemiology of Tuberculosis 50 

High-Risk Groups for TB Disease (2) 

People Living with HIV 

•	 HIV is the strongest known risk factor for
 

developing TB disease
 

•	 TB is the leading cause of death for people
 

with HIV/AIDS
 

•	 Risk of developing TB disease is 7% - 10%
 

each year for people who are infected with
 

both TB and HIV (if the HIV is not treated)
 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection 

Study Question 2.7 

Name 7 groups of people who are more likely to
 

be exposed or infected with M. tuberculosis.
 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection 

Study Question 2.8 

What are public health agencies doing to 

address the high rate of TB in foreign born 

persons? 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection 

Study Question 2.9 

Why is the risk of being exposed to TB 

higher in certain settings, such as nursing 

homes or correctional facilities? 

51 

53 Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

9
 

52 

54 
 

 

 

 

 

High-Risk Groups for TB Infection 

Study Question 2.10 

What are some reasons why rates of TB 

disease are higher in correctional facilities? 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Infection

Study Question 2.11 

 

 

 

 

 

When a child has TB infection or disease, 

what does it tell us about the spread of TB in 

the child’s home or community? Name 3 

things. 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Disease 

Study Question 2.12 

Name 8 groups of people who are more likely to 

develop TB disease once infected. 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Disease

Study Question 2.13 

What is the strongest known risk factor for 

the development of TB disease? 

Module 2 – Epidemiology of Tuberculosis 

High-Risk Groups for TB Disease

Study Question 2.14 

 

 

 

 

 

55 

If a person is infected with both M. 

tuberculosis and HIV, what are his or her 

chances of developing TB disease? How 

does this compare to the risk for people who 

are infected only with M. tuberculosis? 

Module 2 – Epidemiology of Tuberculosis 

Case Studies
 

57 

59 

Module 2 - Epidemiology of Tuberculosis
 

10
 

56 

58 

60 
Person Factors 

a) Mr. Petrov ___ Works at a nursing home 

___ Rides the subway every day 

___ Emigrated from Russia 

b) Ms.Montoya ___ Wasborn in Latin America 

___ Has a father who had pulmonary TB 

disease 

c) Ms. Parker ___ Volunteers in the emergency room of an 

inner-city hospital 

___ Works in a day care center 

d) Mr.Dudley ___ Was released from prison last year 

___ Sleeps in a homeless shelter 

 

 

Person Factors 

a) Mr. Sims ___ Injects heroin 

___ HasHIV 

b) Mr.Allen ___ Hasdiabetes 

___ Hashigh blood pressure 

c) Ms. Li ___ Haschest x-ray findings suggestive of 

previous TB disease 

___ Hasheart problems 

d) Mr.Vinson ___ Isoverweight 

___ Became infected with M. tuberculosis 6 

months ago 

Module 2: Case Study 2.1
 Module 2: Case Study 2.2
 

For each of the following people, choose the factor(s) known to 

increase the risk of being exposed to or infected with TB For each of the following people, indicate the factor(s) known to 

increase the risk of developing TB disease once infected 

Module 2 – Epidemiology of Tuberculosis 61 Module 2 – Epidemiology of Tuberculosis 

Module 2 - Epidemiology of Tuberculosis
 

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