Slide Set — Self Study Modules
Module 2: Epidemiology of TB
Text Only Version
(Title Slide). Self-Study Modules on Tuberculosis: Epidemiology of Tuberculosis
Module 2: Objectives
At completion of this module, learners will be able to:
- Describe how the number of TB cases reported in the U.S has changed over the last 50 years
- List 5 factors that contributed to the increase in the number of TB cases between 1985 and 1992
- List 3 improvements TB programs made with increased federal funds that have contributed to a decrease in TB cases since 1993
- List groups of people who are more likely to be exposed to or infected with M. tuberculosis
- List groups of people who are more likely to develop TB disease once infected with M. tuberculosis
Module 2: Overview
- Epidemiology of TB
- TB Case Rate
- People at High Risk for Becoming Infected with M. Tuberculosis
- People at High Risk for Developing TB Disease after Infection with M. tuberculosis
- Case Studies
(Title Slide). Epidemiology of TB
Epidemiology (1)
Epidemiology is the study of the distribution and causes of disease and other health problems in different groups of people.
Epidemiology (2)
- Epidemiologists:
- Determine frequency and pattern of health problems in communities
- Try to figure out why health problems are occurring
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
- 2 million people die of TB
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
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
U.S. TB Resurgence (1)
There was a 20% increase in the number of TB cases in the United States from 1986 – 1992.
[IMAGE: Graph showing the number of TB cases per year from 1982-2008. The resurgence of TB in the mid-1980s was marked by several years of increasing case counts until its peak in 1992.]
U.S. TB Resurgence (2): 1986 – 1992
- Contributing factors:
- Inadequate funding for TB control programs
- HIV epidemic
- Increased immigration from countries where TB is common
- Spread of TB in homeless shelters and correctional facilities
- Increase and spread of multidrug-resistant TB (MDR TB)
U.S. TB Control and Prevention (1): 1993 - 2008
- 1993 – 2008
- Number of TB cases reported annually in U.S. steadily declined
- Increased federal funds and other resources allowed TB programs to improve their control efforts to:
- Promptly identify persons with TB
- Start appropriate initial treatment for TB cases
- Ensure patients complete treatment
U.S. TB Control and Prevention (2): 1993 – 2008
There was a 50% decrease in the number of TB cases in the United States from 1993 – 2008.
[IMAGE: Graph showing the number of TB cases per year from 1982-2008. Case counts began decreasing again in 1993, and 2008 marked the sixteenth year of decline in the total number of TB cases reported in the United States since the peak of the resurgence. From 1992 until 2002, the total number of TB cases decreased 5%–7% annually. From 2002 to 2003, however, the total number of TB cases decreased by only 1.4%. In 2008, a total of 12,904 cases were reported from the 50 states and the District of Columbia. This represents a decline of 2.9% from 2007 and of approximately 50% from 1992.]
Continuing Challenges in TB Control
- 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 residents
- TB affects racial/ethnic minorities disproportionately
- MDR TB and extensively drug-resistant TB (XDR TB)
Epidemiology of TB: Study Question 2.1
What happened to the number of TB cases in the United States between 1953 and 1984? (pg. 6)
- From 1953 - 1984, the number of TB cases reported in the U.S. decreased by an average of 6% each year.
Epidemiology of TB: Study Question 2.2
What happened to the number of TB cases in the United States between 1985 and 1992? (pg. 6)
- From 1985 - 1992, the number of new TB cases increased by 20%.
Epidemiology of TB: Study Question 2.3
Name five factors that may have contributed to the increase in the number of TB cases between 1985 and 1992 (pg. 6)
- 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., correctional facilities and homeless shelters)
- Spread of MDR TB
Epidemiology of TB: Study Question 2.4
What has been happening to the number of TB cases in the United States since 1993? (p. 6)
- Since 1993, there has been a steady decline in the number of TB cases reported annually in the United States.
Epidemiology of TB: Study Question 2.5
Name 3 improvements TB programs were able to make with increased federal funds that contributed to the decrease in TB cases since 1993. (pg. 6)
- Promptly identify persons with TB
- Start appropriate initial treatment for TB cases
- Ensure patients complete treatment
(Title Slide) TB Case Rate
TB Case Rate (1)
- A case rate is the number of TB cases at a certain place and time, divided by size of the population at that time
- Often expressed in terms of a population size of 100,000 persons
TB Case Rate (2)
Example:
- In the U.S. in 2008, there were 12,904 new TB cases in a population size of 304,059,724
| 12,904 | x 100,000 | = 4.2 |
| 304,059,724 |
- In 2008, the U.S. TB case rate was 4.2 TB cases per 100,000 persons
TB Case Rates by State, United States, 2008
[IMAGE: This map shows TB case rates in the U.S. for 2008. Thirty states had a rate of less than or equal to 3.5 TB cases per 100,000, the interim goal for the year 2000 established by the Advisory Council for the Elimination of Tuberculosis. This group of states has remained fairly constant over the last decade; five states (CT, MI, NM, OR, and PA) joined the group in 2000, one state (MO) joined the group in 2001 (also in 1998 for one year only), and one state (KY) joined the group in 2003. In 2008, five more states (AZ, AR, OK, RI and WA) joined the group but one state (MA) left the group. Eleven states and the District of Columbia (DC) reported a rate above the 2008 national average of 4.2 cases per 100,000: AK, CA, FL, GA, HI, LA, MD, NJ, NY, TN and TX. These 11 states and DC accounted for 67% of the national total and experienced substantial overall decreases in cases and rates from 1992 through 2008, with the exception of a slight increase in the number of cases for MA in 2008 compared to 2007.]
TB Case Rate (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
- Groups with higher rates of TB are considered “high-risk” groups
High-Risk Groups
- High-risk groups can be divided into two categories:
- High risk for becoming infected with M. tuberculosis
- High risk for developing TB disease after infection with M. tuberculosis
(Title Slide). People at High Risk for Becoming Infected with Mycobacterium tuberculosis
People at High Risk for TB Infection
- Close contacts
- Foreign-born persons
- Low-income groups and homeless persons
- Individuals who live and/or work in special settings
- Health care workers who serve high-risk groups
- Racial and ethnic minorities
- Infants, children, and adolescents
- People who inject drugs
High-Risk Groups for TB Infection (1): Close Contacts
- Close contacts are people who spend time with someone who has infectious TB disease
- May include:
- Family members
- Coworkers
- Friends
- On average, 20 - 30% of close contacts become infected with TB
[IMAGE: Two female contacts talking]
High-Risk Groups for TB Infection (2): Foreign-Born Persons
- 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
[IMAGE: Pie chart showing the overall distribution of the countries of birth of foreign-born persons reported with TB in 2008, with the top seven highlighted. The seven top countries accounted for 61% of the total, with Mexico accounting for 23%; the Philippines, 11%; India, 8%; Vietnam, 8%; China, 5%; Guatemala, 3%; and Haiti, 3%. Persons from more than 135 other countries each accounted for 2% or less of the total, but altogether accounted for 38% of foreign-born persons reported with TB.]
High-Risk Groups for TB Infection (3): Foreign-Born Persons
[IMAGE: Two pie graphs. In 1992, 27% of TB cases occurred in foreign-born persons; 73% of TB cases occurred in U.S.-born persons. In 2008, 59% of TB cases occurred in foreign-born persons; 41% occurred in U.S.-born persons.]
High-Risk Groups for TB Infection (4): Foreign-Born Persons
- To address high rates of TB in foreign-born persons, CDC and other public health organizations are:
- Improving the screening process for immigrants and refugees
- Strengthening the notification system that alerts health departments about the arrival of immigrants and refugees with suspected TB disease
- Testing recent arrivals from countries where TB is common for LTBI and ensuring completion of treatment
High-Risk Groups for TB Infection (5): Foreign-Born Persons
- Individuals applying for immigration and refugee status from overseas:
- Must be screened for TB by panel physicians before entering U.S.
- Must have completed treatment before entering U.S. if diagnosed with active TB
High-Risk Groups for TB Infection (6): Foreign-Born Persons
- Immigrants in U.S. applying for permanent residence or citizenship:
- Must be tested for LTBI and evaluated for TB disease by U.S.- based civil surgeons
[IMAGE: A doctor and patient reviewing chest x-ray]
High-Risk Groups for TB Infection (7): Low-Income and Homeless
- Low-income is linked to higher risk of exposure
- Possible reasons include factors associated with low-income:
- Inadequate living conditions
- Crowding
- Malnutrition
- Poor access to health care
- In 2008, 6% of TB patients were homeless
[IMAGE: Homeless man under a bridge]
High-Risk Groups for TB Infection (8): Special Settings
- Special settings include congregate and residential settings:
- Nursing homes
- Correctional facilities
- Health care facilities
- Homeless shelters
- Drug treatment centers
High-Risk Groups for TB Infection (9): Special Settings
- Risk of exposure to TB is higher than in other settings
- Risk is higher if facility is crowded
High-Risk Groups for TB Infection (10): Correctional Facilities
- Higher risk in correctional facilities may be due to:
- Inmates who already have TB infection are at higher risk to develop TB disease
- Increasing number of inmates are infected with HIV
- Overcrowded facilities promoting the spread of TB
High-Risk Groups for TB Infection (11): People Who Inject Drugs
- People who inject drugs are more likely to be exposed to TB, become infected, and develop disease due to certain risk factors:
- Being in correctional facilities or drug treatment centers
- Having poor access to healthcare
- Having a higher risk of HIV infection
- Having a weak immune system due to injecting drugs
High-Risk Groups for TB Infection (12): 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
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 recently
- Person who transmitted TB to child may still be infectious
- Others may have been exposed
High-Risk Groups for TB Infection (14): Racial and Ethnic Minorities
- TB affects certain racial and ethnic minorities disproportionately
- In 2008, about 83% of TB cases in 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 U.S. population
High-Risk Groups for TB Infection (15): Racial and Ethnic Minorities
[IMAGE: Pie chart of reported TB cases by race and ethnicity in the U.S. In 2008, 83% of all reported TB cases occurred in racial and ethnic minorities (29% in Hispanics, 26% in Asians, 25% in non-Hispanic blacks or African-Americans, 1% in American Indians or Alaska Natives, and <1% in Native Hawaiians or Other Pacific Islanders), whereas 17% of cases occurred in non-Hispanic whites. Persons reporting two or more races totaled less than 1% of all cases.]
High-Risk Groups for TB Infection (16): Racial and Ethnic Minorities
[IMAGE: Pie chart of racial and ethnic groups by percentage of U.S. population, 2008. In 2008, the U.S. population was 66% non-Hispanic white; 15% Hispanic or Latino; 12% non-Hispanic black or African American; 4% Asian; 1% Alaskan Indian or Alaskan Native; <1% Native Hawaiian or other Pacific Islander; and 1% two or more races.]
High-Risk Groups for TB Infection (17): Racial and Ethnic Minorities
- 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
Relative Risk for TB (1)
Relative risk is a ratio of the probability of disease occurring in one group versus another group.
Relative Risk for TB (2)
Example:
The case rate for Asians is 25.6 compared to 1.1 in non-Hispanic whites. Therefore, the relative risk for Asians is about 23 times higher than non-Hispanic whites.
To calculate relative risk, 25.6 (TB case rate for Asians) is divided by 1.1 (TB case rate for non-Hispanic whites).
Relative Risk for TB (3): Race and Ethnicity, 2008
Race/Ethnicity |
TB Case Rate |
Relative Risk* |
|---|---|---|
Asians |
25.6 |
23 |
Native Hawaiians or Other Pacific Islanders |
15.9 |
14 |
Blacks or African Americans |
8.8 |
8 |
Hispanics or Latinos |
8.1 |
7 |
American Indians or Alaskan Natives |
6 |
5 |
Non- Hispanic Whites |
1.1 |
1 |
High-Risk Groups for TB Infection: Study Question 2.6
Name eight groups of people who are more likely to be exposed or infected with M. tuberculosis (pg. 16)
- Close contacts of people known/suspected to have TB
- People who came to the U.S. within last 5 years from countries where TB is common
- Low-income groups
- People who live or work in residential facilities
- People who inject drugs
- Health care workers who serve high-risk clients
- High-risk racial or ethnic minority populations
- Infants, children, and adolescents exposed to adults in high-risk groups
High-Risk Groups for TB Infection: Study Question 2.7
What are public health agencies doing to address the high rate of TB in foreign born persons? (pg. 16)
- Improving overseas and domestic screening process of immigrants and refugees
- Strengthening the current notification system that alerts health departments about immigrants or refugees with suspected TB
- Testing recent arrivals from countries where TB is common for LTBI and ensuring completion of treatment
High-Risk Groups for TB Infection: Study Question 2.8
Why is the risk of being exposed to TB higher in certain settings, such as nursing homes or correctional facilities? (pg. 16)
- Many people in these facilities are at risk for TB disease
- Risk of exposure is higher if facility is crowded
High-Risk Groups for TB Infection: Study Question 2.9
What are some reasons why rates of TB disease are higher in correctional facilities? (pg. 16)
- Many inmates already have TB infection and are at a higher risk to develop TB disease
- An increasing number of inmates are infected with HIV, which means they are more likely to develop TB disease if they become infected with TB
- Overcrowded facilities promotes the spread of TB
High-Risk Groups for TB Infection: Study Question 2.10
Which racial and ethnic groups are disproportionately affected by TB? (pg. 17)
- Asians
- Native Hawaiians or Other Pacific Islanders
- Non-Hispanic blacks
- Hispanics
- American Indians or Alaska Natives
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. (pg. 17)
- TB was transmitted recently
- Person who transmitted TB to the child may still be infectious
- Other adults and children in the home or community have probably been exposed to TB
(Title Slide) People at High Risk for Developing TB Disease After Infection with Mycobacterium tuberculosis
High-Risk Groups for TB Disease (1)
- People living with HIV
- People with certain medical conditions that are known to increase the risk for TB
- People infected with M. tuberculosis within the past 2 years
- Infants and children younger than 4 years old
- People who inject drugs
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
High Risk Groups for TB Disease (3): Individuals with Certain Medical Conditions
- Prolonged therapy with corticosteroids, and other immunosuppressive therapy, such as tumor necrosis factor-alpha [TNF-α] antagonists
- Silicosis
- Diabetes
High Risk Groups for TB Disease (4): Individuals with Certain Medical Conditions
- Severe kidney disease
- Certain types of cancer
- Certain intestinal conditions
High Risk Groups for TB Disease (5): Recently Infected
- Individuals infected within the past 2 years are more likely to develop TB disease
- Risk of developing disease in first 2 years is 5%
- Risk over entire lifetime is 10%
High Risk Groups for TB Disease (6): Infants and Children Younger than 4 Years
- Higher risk due to underdeveloped immune system
[IMAGE: Toddler]
High Risk Groups for TB Disease (7): People Who Inject Drugs
- Higher risk of developing TB disease once infected due to:
- Greater possibility of HIV infection
- Injecting drugs may weaken immune system
High Risk Groups for TB Disease: Study Question 2.12
Name five groups of people who are more likely to develop TB disease once infected (pg. 21)
- People living with HIV
- People with certain medical conditions
- People infected with M. tuberculosis within the past 2 years
- Infants and children younger than 4 years old
- People who inject drugs
High Risk Group for TB Disease: Study Question 2.13
What is the strongest known risk factor for the development of TB disease? (pg. 21)
- HIV infection is the strongest known risk factor for developing TB disease. HIV infection weakens the body’s immune system, making it more likely for a person who has TB infection to develop TB disease.
High Risk Group for TB Disease: Study Question 2.14
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? (pg. 21)
- 7% - 10% each year if infected with both M. tuberculosis and HIV
- 10% over a lifetime if only infected with M. tuberculosis
(Title Slide) Case Studies
Module 2: Case Study 2.1
For each of the following people, indicate the factor(s) known to increase the risk of being exposed to or infected with TB:
- Mr. LeFevre
- Works at a nursing home (risk factor)
- Immigrated from Russia (risk factor)
- Rides the subway every day (not a risk factor)
- Ms. Montoya
- Was born in Latin America (risk factor)
- Has a father who had pulmonary TB disease (risk factor)
- Ms. Parker
- Volunteers in the emergency room of an inner-city hospital (risk factor)
- Works in a day care center (not a risk factor)
- Mr. Dudley
- Was released from prison last year (risk factor)
- Sleeps in a homeless shelter (risk factor)
Module 2: Case Study 2.2
For each of the following people, indicate the factor (s) known to increase the risk of being exposed to or infected with TB:
- Mr. Sims
- Injects heroin (risk factor)
- Is infected with HIV(risk factor)
- Mr. Allen
- Has diabetes (risk factor)
- Has high blood pressure (not a risk factor)
- Ms. Li
- Has chest x-ray findings suggestive of previous TB disease (risk factor)
- Has heart problems (not a risk factor)
- Mr. Vinson
- Is obese (not a risk factor)
- Became infected with M. tuberculosis 6 months ago (risk factor
Contact Us:
- Centers for Disease Control and Prevention
Division of Tuberculosis Elimination (DTBE)
1600 Clifton Rd., NE
MS E10
Atlanta, GA 30333 - 800-CDC-INFO
(800-232-4636)
TTY: (888) 232-6348 - New Hours of Operation
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Closed Holidays - cdcinfo@cdc.gov
