Self-Study Modules on Tuberculosis, 1-5 

Centers for Disease Control and Prevention

Division of Tuberculosis Elimination

2016

1

Introduce yourself to participants.  Include your name and what organization you represent. 

Ask participants to introduce themselves, stating their names and organizations

Provide information about the following: 

Location of restrooms

Refreshments, if provided

Discuss ground rules and the parking lot

Ask participants to sign participant roster

  CDC Self-Study Modules on Tuberculosis, 1-5 

Module 1: Transmission and Pathogenesis of TB

Module 2: Epidemiology of TB

Module 3: Targeted Testing and the Diagnosis of Latent TB Infection and TB Disease 

Module 4: Treatment of Latent TB Infection and TB Disease

Module 5:  Infectiousness and Infection Control

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Explain to participants that the presentations were created using the print-based Self-Study Modules on Tuberculosis, 1-5 

Ask who has worked through the print-based modules before

Review slide content

Mention that each module includes content about that topic

State that study questions and case studies are included in each module to help reinforce and apply content

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Self-Study Modules on Tuberculosis

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Transmission andPathogenesis of Tuberculosis

Introduce Module 1

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Module 1: Objectives

At completion of this module, learners will be

able to

Describe the history of tuberculosis (TB).

Explain how TB is spread (transmission).

Define drug-resistant TB.

Explain the difference between latent TB infection (LTBI) and TB disease.

Explain how LTBI and TB disease develop (pathogenesis).

Describe the classification system for TB.

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State objectives of  presentation 

 Background and Objectives -  Module 1, p. 1

Module 1 – Transmission and Pathogenesis of Tuberculosis

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History of TB

TB Transmission

Drug-Resistant TB 

TB Pathogenesis

Progression from LTBI to TB disease

Sites of TB disease

TB Classification System

Case Studies

Module 1: Overview

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Review slide content 

History of TB

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Introduce section

History of TB - Module 1, pp. 5-6

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB has affected humans for millennia

Historically known by a variety of names, including:

Consumption

Wasting disease

White plague

TB was a death sentence for many

History of TB (1)

Vintage image circa 1919

Image credit: National Library of Medicine 

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Before showing slide, ask participants if they know of other names for TB

Review slide content

History of TB - Module 1, p. 5

[Image credit:  U.S. National Library of Medicine]

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Until mid-1800s, many believed TB was hereditary

1865 Jean Antoine-Villemin showed TB was contagious

1882 Robert Koch discovered M. tuberculosis, the bacterium that causes TB 

Mycobacterium tuberculosis

Image credit: Janice Haney Carr

History of TB (2)Scientific Discoveries in 1800s

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Review slide content

Note that the image is of Mycobacterium tuberculosis 

History of TB - Module 1, p. 5

[Image credit: Janice Haney Carr]

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Before TB antibiotics, many patients were sent to sanatoriums

Patients followed a regimen of bed rest, open air, and sunshine

TB patients who could not afford sanatoriums often died at home

History of TB (3)Sanatoriums

Sanatorium patients resting outside

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Review slide content 

Explain that the image is of women at a sanatorium resting outside

Note that it used to be believed that cool, fresh air was beneficial for TB patients

History of TB - Module 1, p. 5

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Breakthrough in the Fight Against TB (1)

Drugs that could kill TB

bacteria were discovered

in 1940s and 1950s

Streptomycin (SM) discovered in 1943

Isoniazid (INH) and

    p-aminosalicylic acid (PAS) discovered between 1943 and 1952 

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Review slide content 

History of TB - Module 1, p. 5

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Breakthrough in the Fight Against TB (2)

TB death rates in U.S. began to drop dramatically

Each year, fewer people died from TB

Most TB sanatoriums in U.S. had closed by mid 1970s

Review slide content 

Mention that as the number of cases and deaths declined, many people began to hope that TB could be eliminated from the U.S., like smallpox and polio

History of TB - Module 1, p. 5

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Resurgence

Increase in TB in mid 1980s

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

March 16, 1992 Newsweek Magazine Cover

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Before showing the slide, ask participants why there was an increase in TB in the U.S. during the mid 1980s

Review slide content 

TB Resurgence  - Module 1, p. 5 and Module 2, p. 4

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Increased governmental funding for TB control programs began in 1992

Number of TB cases declined from 1993 to 2014

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

TB Prevention and Control Efforts

Year

No. of Cases

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Review slide content

Point out the increase (1980s) and decrease (after 1993) in TB cases on the graph

Stress that prevention and control efforts must be maintained since TB continues to be reported in almost every state and not all states have seen a decrease in TB cases

TB Prevention and Control Efforts - Module 2, pp. 4-5

Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB History Timeline

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Recap the major events in the history of TB

TB History Timeline - Module 1, p. 6

Module 1 – Transmission and Pathogenesis of Tuberculosis

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     In what year was each of the following

    discoveries made? 

TB was shown to be contagious 

	1865

The bacterium that causes TB was discovered

	1882

The first drug that could kill TB bacteria was discovered

	1943

History of TBStudy Question 1.1

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Introduce study questions 

Ask participants to turn to p. 6 (if participants have print-based modules)

Ask for a volunteer to read question 

Ask participants for answers

Click enter for the answer to appear

Note: All study questions and case studies are animated.  The question appears first. Click “enter” and the answer will appear.

Answers – Module 1, p. 26

TB Transmission

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Introduce section

Ask participants how TB is transmitted

TB Transmission - Module 1, pp. 7-8

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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

TB Transmission (1)

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Ask for a volunteer to read the definition of transmission 

Definition of Transmission – Module 1, p. 7

Module 1 – Transmission and Pathogenesis of Tuberculosis

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M. tuberculosis causes most TB cases in U.S.

Mycobacteria that cause TB:

M. tuberculosis 

M. bovis

M. africanum

M. microti

M. canetti

Mycobacteria that do not cause TB

e.g., M. avium-complex

  M. tuberculosis

TB Transmission (2)Types of Mycobacteria

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State that mycobacteria are members of the bacteria family

Explain that not all mycobacteria cause TB

Review slide content

Types of Mycobacteria - Module 1, p. 7

Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB is spread person to person through the air via droplet nuclei

M. tuberculosis may be expelled when an infectious person:

Coughs

Speaks  

Sings

Transmission occurs when another person inhales droplet nuclei

TB Transmission (3)

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Review slide content

Note that droplet nuclei are very small particles, less than 1/5,000 of an inch, and can remain suspended in the air for several hours

Emphasize that transmission is more likely to occur in poorly ventilated and enclosed areas

TB Transmission - Module 1, p. 7

Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Transmission (4)

Dots in air represent droplet nuclei containing

M. tuberculosis

Note that this image depicts airborne transmission. The individual on the left has infectious TB disease and is expelling it into the air. The individual on the right is inhaling the droplet nuclei into their lungs.

Note: Dots in the image are animated.  Click “enter” once to start animation.

TB Transmission - Module 1, p. 8

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Probability that TB will be transmitted depends on:

Infectiousness of the TB patient

Environment in which the exposure occurred

Frequency and duration of the exposure

Susceptibility (immune status) of the exposed individual

The best way to stop transmission is to:

Isolate infectious persons

Provide treatment to infectious persons as soon as possible

TB Transmission (5)

Emphasize that not everyone who is exposed to TB becomes infected; it depends on many factors

Review slide content

Note that the length of time required for a patient to be considered noninfectious after starting treatment varies

TB Transmission - Module 1, p. 8

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB TransmissionStudy Question 1.2

    What organism causes TB?

	M. tuberculosis

    What are four other tuberculous mycobacteria?

M. bovis, M. africanum, M. microti, and M.

canetti

22

Introduce study questions

Ask participants to turn to p. 10 (if participants have print-based modules)

Ask for a volunteer to read question 

Ask participants for answers

Answers – Module 1, p. 26

Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB TransmissionStudy Question 1.3

	How is TB spread? 

	TB is spread from person to person through the air via droplet nuclei containing M. tuberculosis.

Read question 

Ask participants for answers

Answers – Module 1, p. 26

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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	The probability that TB will be transmitted depends on what four factors? 

Infectiousness of the TB patient

Environment in which exposure occurred

Frequency and duration of the exposure

Susceptibility (immune status) of the exposed individual

TB TransmissionStudy Question 1.4

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Read question 

Ask participants for answers

 Answers – Module 1, p. 26

Drug-Resistant TB

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Introduce section

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Caused by M. tuberculosis organisms resistant to  at least one TB treatment drug 

Resistant means drugs can no longer kill the bacteria

Drug-Resistant TB (1)

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Review slide content 

Note that drug-resistant TB is more difficult to treat because there are fewer treatment options

Drug-Resistant TB - Module 1, p. 9

Module 1 – Transmission and Pathogenesis of Tuberculosis

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| Mono-resistant                      | Resistant to any one TB treatment drug                                                                                                                                  |
|-------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Poly-resistant                      | Resistant to at least any 2 TB drugs (but not both isoniazid and rifampin)                                                                                              |
| Multidrug- resistant (MDR TB)       | Resistant to at least isoniazid and rifampin, the 2 best first-line TB treatment drugs                                                                                  |
| Extensively drug-resistant (XDR TB) | Resistant to isoniazid and rifampin, PLUS resistant to any fluoroquinolone AND at least 1 of the 3 injectable anti-TB drugs (e.g., amikacin, kanamycin, or capreomycin) |

Drug-Resistant TB (2)

Review slide content

Note that XDR TB is the most difficult type of drug-resistant TB to treat

Explain that patients with drug-resistant TB should be closely monitored to see if they are responding to treatment; they should also remain in isolation until they are no longer infectious

Drug-Resistant TB - Module 1, p. 9

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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| Primary Resistance              | Caused by person-to-person transmission of drug-resistant organisms                                                                                 |
|---------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------|
| Secondary Resistance (acquired) | Develops during TB treatment: Patient was not treated with an   appropriate regimen   OR  Patient did not follow treatment    regimen as prescribed |

Drug-Resistant TB (3)

State that drug-resistant TB can be caused in two ways, primary and secondary

Review slide content

Note that drug-resistant TB can be transmitted in the same way as drug-susceptible TB; however, because it takes longer to diagnose, patients with drug-resistant TB may be infectious for longer periods of time

Drug-Resistant TB - Module 1, p. 9

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Drug-resistant TBStudy Question 1.5

	What is drug-resistant TB? 

		Drug-resistant TB is caused by M. 	tuberculosis organisms that are resistant 	to at least one anti-TB drug.  

		Drug-resistant TB can be difficult to treat.

Introduce study questions

Ask participants to turn to p. 10 (if participants have print-based modules)

Ask  for a volunteer to read question 

Ask participants for answers

Answers – Module 1, p. 26

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Drug-resistant TBStudy Question 1.6

	What is the difference between primary and secondary drug resistance? 

Primary resistance is caused by person-to-person transmission of drug-resistant organisms. 

Secondary resistance develops during TB treatment.  Either the patient was not treated with the right TB drugs or the patient did not follow the prescribed treatment regimen. 

Read question 

Ask participants for answers

 Answers – Module 1, p. 26

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TB Pathogenesis

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Introduce section

Ask participants if they can explain pathogenesis

TB Pathogenesis - Module 1, p. 11

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Pathogenesis is defined as the way an infection or disease develops in the body.

TB Pathogenesis (1)

Ask for a volunteer to read the definition of pathogenesis 

TB Pathogenesis - Module 1, p. 11

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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LTBI occurs when tubercle bacilli are in the body, but the immune system is keeping them under control

LTBI is detected by the Mantoux tuberculin skin test (TST) or by an interferon-gamma release assay (IGRA), such as:

QuantiFERON®-TB Gold In-Tube (QFT-GIT)

T-Spot®.TB test (T-SPOT)

People with LTBI are NOT infectious

TB Pathogenesis (2)Latent TB Infection (LTBI)

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Review slide content

LTBI – Module 1, p. 12

Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB disease develops when the immune system cannot keep tubercle bacilli under control

May develop very soon after infection or many years after infection

About 10% of all people with normal immune systems who have LTBI will develop TB disease at some point in their lives

People with TB disease are often infectious

TB Pathogenesis (3)TB Disease

Review slide content 

TB Disease – Module 1 p. 16

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Pathogenesis (4)

Droplet nuclei containing tubercle bacilli are inhaled, enter the lungs, and travel to small air sacs (alveoli)

Review slide content 

Explain that the dots in the air represent droplet nuclei being inhaled into the person’s lungs

TB  Pathogenesis – Module 1 p. 16

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Pathogenesis (5)

Tubercle bacilli multiply in alveoli, where 

infection begins 

Review slide content 

TB Pathogenesis – Module 1 p. 16

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Pathogenesis (6)

A small number of tubercle bacilli enter bloodstream and spread throughout body

Review slide content

State that tubercle bacilli can reach any part of the body, but areas where TB disease is more likely to develop include:

Lungs

Kidneys

Brain 

Bones

TB Pathogenesis – Module 1, p. 17

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Pathogenesis (7)LTBI

Within 2 to 8 weeks the immune system produces special immune cells called macrophages that surround the tubercle bacilli

These cells form a barrier shell that keeps the bacilli contained and under control (LTBI)

38

Review slide content 

Call attention to the barrier shell around the bacilli that is keeping the tubercle bacilli contained (upper left corner of figure)

TB Pathogenesis – Module 1, p. 17

Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Pathogenesis (8)TB Disease

If the immune system CANNOT keep tubercle bacilli under control, bacilli begin to multiply rapidly and cause TB disease

This process can occur in different places in the body

39

Review slide content 

Explain that the barrier shell around the bacilli has broken (upper left corner of figure)

Note: The red circle around broken barrier shell is animated.  Click “enter” for the circle to appear.

TB  Pathogenesis – Module 1, p. 17

| Person with LTBI                                                                         | Person with TB Disease (in the lungs)                                    |
|------------------------------------------------------------------------------------------|--------------------------------------------------------------------------|
| Has a small number of TB bacteria in his or her body that are alive, but under control   | Has a large number of active TB bacteria in his or her body              |
| Cannot spread TB bacteria to others                                                      | May spread TB bacteria to others                                         |
| Does not feel sick, but may become sick if the bacteria become active in his or her body | May feel sick and may have symptoms such as cough, fever, or weight loss |
| TST or IGRA results usually positive                                                     | TST or IGRA results usually positive                                     |
| Chest x-ray usually normal                                                               | Chest x-ray usually abnormal                                             |

Module 1 – Transmission and Pathogenesis of Tuberculosis

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LTBI vs. TB Disease (1)

Review each row of the table, comparing LTBI and TB disease

Refer participants to p. 12 to follow along

LTBI vs. TB Disease – Module 1, p. 12

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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LTBI vs. TB Disease (2)
| Person with LTBI                                         | Person with TB Disease (in the lungs)      |
|----------------------------------------------------------|--------------------------------------------|
| Sputum smears and cultures negative                      | Sputum smears and cultures may be positive |
| Should consider treatment for LTBI to prevent TB disease | Needs treatment for TB disease             |
| Does not require respiratory isolation                   | May require respiratory isolation          |
| Not a case of TB                                         | A case of TB                               |

Review each row of the table, comparing LTBI and TB disease

Refer participants to p. 12 to follow along

LTBI vs. TB Disease – Module 1, p. 12

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB PathogenesisStudy Question 1.7

	When a person inhales droplet nuclei containing M. tuberculosis, where do the droplet nuclei go?

Most of the larger droplet nuclei become lodged in the upper respiratory tract, where infection is unlikely to develop

However, droplet nuclei may reach the small air sacs of the lung (the alveoli), where infection may begin

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 Introduce study questions

Ask participants to turn to p. 13 (if participants have print-based modules)

Ask for a volunteer to read question 

Ask participants for answers

Answers – Module 1, p.  26

Module 1 – Transmission and Pathogenesis of Tuberculosis

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	After the tubercle bacilli reach the small air sacs of the lung (the alveoli), what happens to the tubercle bacilli? 

Tubercle bacilli multiply in alveoli and some enter the lymph nodes and bloodstream and spread throughout the body  

Bacilli may reach any part of the body

Within 2 to 8 weeks, the immune system usually intervenes, halting multiplication and preventing further spread

TB PathogenesisStudy Question 1.8

Ask for a volunteer to read question

Ask participants for answers

Answers – Module 1, p. 27

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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	In people with LTBI (but not TB disease), how does the immune system keep the tubercle bacilli under control? 

		The immune system produces special 	immune cells that surround the tubercle 	bacilli. The cells form a shell that keeps 	the bacilli contained and under control.	

TB PathogenesisStudy Question 1.9

Ask for a volunteer to read question 

Ask participants for answers

Answers – Module 1, p.  27

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB PathogenesisStudy Question 1.10

     How is LTBI detected? 

	LTBI is detected by the Mantoux tuberculin skin test (TST) or blood tests such as interferon-gamma release assays (IGRAs), which include the QuantiFERON®-TB Gold In-tube (QFT-GIT) or the T-SPOT®.TB test (T-SPOT). 

Ask participants to turn to p. 16 (if participants have print-based modules)

Read question 

Ask participants for answers

Answers – Module 1, p.  27

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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	What are the major similarities and differences between LTBI and TB disease? List characteristics of each. 

TB PathogenesisStudy Question 1.11

Read question 

Ask participants for answers

Answers – Module 1, pp. 27-28

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB PathogenesisStudy Question 1.12

	What happens if the immune system cannot keep the tubercle bacilli under control and the bacilli begin to multiply rapidly? 

		When this happens, TB disease 	develops.  The risk that TB disease will 	develop is higher for some people than 	for others.

47

Read question 

Ask participants for answers

Answers – Module 1, p. 28

TB Pathogenesis

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Progression from LTBI to TB Disease 

Introduce section 

Progression from LTBI to TB Disease – Module 1, pp. 18-19

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Progression to TB Disease (1)

Risk of developing TB disease is highest the first 2 years after infection 

People with LTBI can be given treatment to prevent them from developing TB disease

Detecting TB infection early and providing treatment helps prevent new cases of TB disease 

Review slide content 

Explain that since the risk of progressing to TB disease is the highest in the first two years after infection, it is important to detect TB infection early 

Progression to TB Disease – Module 1, p. 18

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Infection with HIV

History of untreated or inadequately treated TB disease

Recent TB infection (within the past 2 years)

Immunosuppressive therapy such as tumor necrosis factor-alpha (TNF) antagonists, systemic corticosteroids, or immunosuppressive drug therapy following organ transplantation

Abusing drugs or alcohol or smoking cigarettes

Silicosis

Diabetes mellitus

Chronic renal failure

Certain types of cancer (e.g., leukemia, cancer of the head, neck, or lung)

Certain intestinal conditions

Low body weight

Some conditions increase probability of LTBI progressing to TB disease

Progression to TB Disease (2)

Review slide content

Tell participants that some of these terms can be found in the glossary of print-based Module 1, pp. 2-4

Progression to TB Disease – Module 1, pp. 18-19

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Progression to TB Disease (3)

Review slide content

Emphasize that not everyone exposed to TB becomes infected with TB, and not everyone that becomes infected with TB develops TB disease

Progression to TB Disease – Module 1, p. 18

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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In an HIV-infected person,

TB can develop in one of

two ways:

Person with LTBI becomes infected with HIV and then develops TB disease as the immune system is weakened

Person with HIV infection becomes infected with M. tuberculosis and then rapidly develops TB disease

Progression to TB Disease (4) TB and HIV

Image credit: Mississippi State Department of Health

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Before showing slide, ask participants what is the strongest known risk factor for the progression of TB disease in people with TB infection

Note that worldwide TB is responsible for the deaths of 1 in 3 people living with HIV/AIDS; making it the leading cause of death for people infected with HIV

Review slide content 

TB and HIV – Module 1, p. 19

[Image credit:  Mississippi State Department of Health]

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Progression to TB Disease (5)TB and HIV

People who are infected with both M. tuberculosis and HIV are much more likely to develop TB disease

Review slide content

Ask why the risk is so much greater with HIV infection

TB and HIV – Module 1, p. 19

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Progression to TB DiseaseStudy Question 1.13

	What percentage of people who have LTBI (but not HIV infection) usually develop TB disease? 

About 10% of all people with LTBI will develop TB disease at some point

In U.S., about 5% of recently infected will develop TB disease in first year or two after infection  

Additional 5% will develop disease later in life

Remaining 90% will remain free of disease for the rest of their lives

Introduce study questions 

Ask participants to turn to p. 20 (if participants have print-based modules)

Ask for a volunteer to read question 

Ask participants for answers

Answers – Module 1, p. 28

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Progression to TB DiseaseStudy Question 1.14

	What conditions appear to increase the risk that LTBI will progress to TB disease? 

Infection with HIV

History of untreated or inadequately treated TB disease

Recent TB infection (within the past 2 years)

Immunosuppressive therapy such as tumor necrosis factor-alpha (TNF) antagonists, systemic corticosteroids, or immunosuppressive drug therapy following organ transplantation

Abusing drugs or alcohol or smoking cigarettes

Silicosis

Diabetes mellitus

Chronic renal failure

Certain types of cancer (e.g., leukemia, cancer of the head, neck, or lung)

Certain intestinal conditions

Low body weight

Ask for a volunteer to read question 

Ask participants for answers

Answers – Module 1, pp. 28-29

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Progression to TB DiseaseStudy Question 1.15

How does being infected with both M. tuberculosis

and HIV affect the risk for TB disease? 

Much more likely to develop TB disease

Risk of developing TB disease is 7% to 10% EACH YEAR (if HIV is not being treated)

In an HIV-infected person, TB disease can develop in two ways:

Person with LTBI becomes infected with HIV and then develops TB disease as the immune system is weakened

Person with HIV infection becomes infected with M. tuberculosis and then rapidly develops TB disease

56

Ask for a volunteer to read question 

Ask participants for answers

Answers – Module 1, p. 29

TB Pathogenesis

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Sites of TB Disease

Introduce section

Note that some patients who have extrapulmonary TB also have pulmonary TB

Sites of TB Disease, Module 1, p. 22

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Sites of TB Disease (1)

Bacilli may reach any part of the body, but common sites include:

Review slide content 

Sites of TB Disease – Module 1, p. 22

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Sites of TB Disease (2)
|                   | Location                                                                                  | Frequency                                                                             |
|-------------------|-------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------|
| Pulmonary TB      | Lungs                                                                                     | Most TB cases are pulmonary                                                           |
| Extrapulmonary TB | Places other than lungs such as: Larynx Lymph nodes Pleura Brain Kidneys Bones and joints | Found more often in: HIV-infected or  other  immunosuppressed  persons Young children |
| Disseminated TB   | Carried to all parts of body, through bloodstream                                         | Rare                                                                                  |

Review slide content

Note that disseminated TB is rare, but very serious

Sites of TB Disease – Module 1, p. 22

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Sites for TBStudy Question 1.16

   What part of the body is the most common

   site for TB disease? 

Lungs are the most common site

   What are some other common sites? 

	-  Larynx

	-  Lymph nodes

	-  Pleura (membrane around the lungs)

	-  Brain

	-  Kidneys

	-  Bones and joints

Introduce study questions 

Ask participants to turn to p. 24 (if participants have print-based modules)

Ask for a volunteer to read question

Ask participants for answers

Answers – Module 1, p. 29

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TB Pathogenesis

Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Classification System

Introduce section

TB Classification System Module 1, p. 23

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Classification System (1)
| Class | Type                                | Description                                                                                                                              |
|-------|-------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------|
| 0     | No TB exposureNot infected          | No history of TB exposureNegative result to a TST or to an IGRA                                                                          |
| 1     | TB exposureNo evidence of infection | History of TB exposureNegative result to a TST or an IGRA (done at least 8 to 10 weeks after exposure)                                   |
| 2     | TB infection No TB disease          | Positive result to a TST or to an IGRA Negative smears, molecular tests, and cultures No clinical or x-ray evidence of active TB disease |

Based on pathogenesis of TB

Review slide content 

State that this classification system is sometimes referred to as the American Thoracic Society (ATS) classification system 

TB Classification System – Module 1, p. 23

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Classification System (2)
| Class | Type                                       | Description                                                                                                                                                                                                       |
|-------|--------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 3     | TB, clinically active                      | Positive culture for M. tuberculosis ORPositive result to a TST or to an IGRA, and clinical, bacteriological, or x-ray evidence of current active TB disease                                                      |
| 4     | Previous TB disease(not clinically active) | Medical history of TB diseaseAbnormal but stable x-ray findings Positive result to a TST or to an IGRA Negative smears, molecular tests, and cultures (if done)No clinical or x-ray evidence of active TB disease |
| 5     | TB suspected                               | Signs and symptoms of TB disease, but diagnostic evaluation not complete                                                                                                                                          |

Based on pathogenesis of TB

Review slide content

State that any TB patient with a classification of 3 or 5 should receive treatment for TB, and should be reported to the health department

TB Classification System – Module 1, p. 23

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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TB Classification SystemStudy Question 1.17

	What is the classification system for TB based on? What is it used for? 

		The current classification system is 	based on the pathogenesis of TB.  Many 	health departments and private health 	care 	providers use this system when 	describing patients.

Ask participants to turn to p. 24 (if participants have print-based modules)

Read question 

Ask participants for answers

Answers – Module 1, p. 29

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Case Studies

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Introduce case studies

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Module 1 – Transmission and Pathogenesis of Tuberculosis

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Module 1: Case Study 1.1 (1)

A 30-year-old man visits the health department for a TST because he is required to have one before starting his new job as a health care worker.  He has an 18 mm positive reaction to the TST.  He has no symptoms of TB, and his chest x-ray findings are normal. 

Ask participants turn to p. 15 (if participants have print-based modules)

Read case study 

Case Study 1.1 – Module 1, p. 15

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Module 1: Case Study 1.1 (2)

Should this be considered a case of TB?

	No. The man described above has LTBI. He has 	an 18 mm positive reaction to the TST, but no 	evidence of TB disease. Therefore, this is not a 	case of TB.

Should this man be considered infectious?

	No, he should not be considered infectious. This 	man has LTBI, not TB disease. People with TB 	infection and no evidence of TB disease are not 	infectious. 

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Read questions 

Ask participants for answers

Answers – Module 1, p. 30

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Module 1: Case Study 1.2 (1)

A 45-year-old woman is referred to the health department by her private physician because she was found to have LTBI as part of an employee testing program. She is overweight, with high blood pressure. Upon further questioning, she reports that she has injected illegal drugs in the past, but has never been tested for HIV infection.

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Ask participants turn to p. 21 (if participants have print-based modules)

Read case study 

Case Study 1.2 – Module 1, p. 21

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Module 1: Case Study 1.2 (2)

What conditions does this woman have that increase the risk that she will develop TB disease?

Drug abuse increases the risk that LTBI will progress to TB disease. This woman may also be at risk for HIV infection because of her injection drug use. HIV is the strongest known risk factor for developing TB disease. This woman should be offered HIV counseling, testing, and referral. Overweight and high blood pressure are NOT risk factors for TB disease.

Module 1 – Transmission and Pathogenesis of Tuberculosis

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Read case study question 

Ask participants for answers 

Ask if there are any questions about Module 1 before moving on to Module 2

Answers – Module 1, p. 30

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