Page 196 - fourth year book

COMMUNICABLE DISEASES (T.B)

Types of TB Infection in humans

Not everyone infected with TB bacteria becomes sick. As a result,
two TB-related conditions exist:

1- Latent TB Infection

Exposure to TB bacteria bur remain dormant or inactive in the
body due to the immune response which fight the bacteria and stop its
growing. However, if TB bacteria become active in the body and
multiply, the person will change from having latent TB infection to TB
disease.

2- TB Disease

Occurs by active multiplication of the TB bacteria in the body to
cause disease and tissue destruction due to weakness of the immune
system.

Difference between latent TB infection and TB disease

Latent TB disease TB disease

• Has small amount of TB • Has large amount of active TB
bacteria in the body that are
alive but not active bacteria in the body

• Tuberculin skin test results • Tuberculin skin test results
usually positive usually positive

• Chest X ray usually normal • Chest X ray usually abnormal

• Sputum smears and cultures • Sputum smears and cultures
negative may be positive

• Has symptoms as cough,
• No symptoms
fever…..
• Often infectious before
• Not infectious
treatment

• Not a case of TB • A case of TB

• Need treatment of LTB • Need treatment to treat TB

infection to prevent TB disease disease

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