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Education Materials > Publications > Self-Study Modules on TB > Module 2 > Background

Self-Study Modules on Tuberculosis

This is an archived document. The links are no longer being updated.

Module 2: Epidemiology of Tuberculosis


Epidemiology is the study of diseases and other health problems in groups of people. Epidemiologists determine the frequency and pattern (the distribution) of health problems in different communities. In other words, they find out who has a specific health problem, how often the problem occurs, and where the problem occurs. Using this information about who, when, and where, epidemiologists try to determine why the health problem is occurring.

Public health officials use epidemiologic information to design ways to prevent and control the diseases in the community. By finding out who is at risk for a specific health problem, they can target their prevention and control strategies at people who are at risk.

This module examines recent trends in TB in the United States and describes groups of people who are at higher risk for TB infection and TB disease.Groups of people who are at higher risk for TB vary from area to area; state and local health departments are responsible for determining specifically who is at risk in their area.


After working through this module, you will be able to:
  1. Describe how the number of TB cases reported in the United States has changed recently.
  2. List four factors that have contributed to the increase in the number of TB cases.
  3. List the groups of people who are more likely to be exposed to or infected with M. tuberculosis.
  4. List the groups of people who are more likely to develop TB disease once infected.
  5. Describe the evidence that suggests that the HIV epidemic has contributed to the increase in the number of TB cases.
  6. List the racial and ethnic groups that are disproportionately affected by TB.
  7. Explain what TB disease in children indicates about the spread of TB in homes and communities.

New Terms

Look for the following new terms in this module and in the glossary.

case rate the number of cases that occur during a certain time period, divided by the size of the population during that time period; the case rate is often expressed in terms of a population size of 100,000 persons

case reporting informing the state or local health department when a new case (an occurrence) of TB disease has been diagnosed or is suspected

close contacts people who spend time with someone who has infectious TB disease

contact investigation a procedure for interviewing a person who has TB disease to determine who may have been exposed to TB. People who have been exposed to TB are screened for TB infection and disease.

epidemiology the study of the distribution and causes of disease and other health problems in different groups of people

foreign-born persons people born outside of the United States; foreign-born persons from areas of the world where TB is common (for example, Asia, Africa, Latin America, and the Caribbean) are more likely to become exposed to and infected with M. tuberculosis

health care facilities places where people receive health care, such as hospitals or clinics

infection control procedures measures to prevent the spread of TB

residential facilities institutions where people live, such as nursing homes, correctional facilities, or homeless shelters


Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination -

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