Lesson 2: TB Transmission and the Development of TB Disease

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Differences Between Latent TB Infection and TB Disease

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Persons with Latent TB Infection (LTBI):

Do not feel sick
Do not have any symptoms
Cannot spread TB bacteria to others
Can have latent TB infection for years
Are at risk for developing TB disease
Have a small amount of TB germs in their body that are alive but inactive
Usually have a positive TB blood test (interferon-gamma release assay [IGRA]) or TB skin test (Mantoux tuberculin skin test [TST]) result indicating TB infection
Should consider treatment for LTBI to prevent TB disease

Persons with TB Disease:

Usually feel sick
Usually have one or more symptoms
May be able to spread TB bacteria to others
Have a large amount of active TB germs in their body
Usually have a positive TB skin test or TB blood test result indicating TB infection
Need treatment for TB disease

A man (on the left) coughing and feeling sick with TB disease. A man (on the right) smiling with LTBI and not feeling sick.

Persons with latent TB infection do not feel sick and cannot spread TB bacteria to others. Persons with TB disease usually feel sick and may be able to spread TB bacteria to others.