TB bacteria become active if the immune system can't stop them
from growing. The active bacteria begin to multiply in the body
and cause TB disease. Some people develop TB disease soon after
becoming infected, before their immune system can fight the TB
bacteria. Other people may get sick later, when their immune system
becomes weak for some reason. Babies and young children often
have weak immune systems. People infected with HIV, the virus
that causes AIDS, have very weak immune systems. Other people
can have weak immune systems, too, especially people with any
of these conditions:
* substance abuse
* diabetes mellitus
* silicosis
* cancer of the head or neck
* leukemia or Hodgkin's disease
* severe kidney disease
* low body weight
* certain medical treatments (such as corticosteroid treatment
or organ transplants)
Symptoms of TB depend on where in the body the TB bacteria are
growing. TB bacteria usually grow in the lungs. TB in the lungs
may cause a bad cough that lasts longer than 2 weeks, pain in
the chest, and coughing up blood or sputum (phlegm from deep inside
the lungs).
Other symptoms of TB disease are:
* weakness or fatigue
* weight loss
* no appetite
* chills
* fever
* sweating at night
For information on how TB disease is treated, see the section
on TB disease.
