Some people develop TB disease soon after becoming infected (within weeks) before their immune system can fight the TB bacteria. Other people may get sick years later, when their immune system becomes weak for another reason.
Overall, about 5 to 10% of infected persons who do not receive treatment for latent TB infection will develop TB disease at some time in their lives. For persons whose immune systems are weak, especially those with HIV infection, the risk of developing TB disease is much higher than for persons with normal immune systems.
Generally, persons at high risk for developing TB disease fall into two categories:
- Persons who have been recently infected with TB bacteria
- Persons with medical conditions that weaken the immune system
How tuberculosis is spread
The difference between active and latent TB disease
People infected with TB bacteria may not get sick because their bodies are able to fight off the infection. This is called latent or inactive TB, and is not infectious.
People who are infected with the TB bacteria that multiplies and grows where the immune system is not able to fight off the bacteria are said to have active TB. These people will have symptoms and are infectious.
High-risk groups of tuberculosis
You are most at risk if you:
- Have been recently infected with TB bacteria, including people who work close to someone with active TB, who live in countries where there is a lot of TB, and young children.
- Have a medical condition that weakens your immune system, like HIV or AIDS, diabetes and some cancers.
People with TB can:
- feel tired and unwell
- have a bad cough that last at least three weeks
- lose weight
- have a fever and sweat in bed at night
- cough up blood in the sputum
- chest pains
- swollen lymph glands.
Nurse reading a patient's skin test There are two kinds of tests that are used to detect TB bacteria in the body: the TB skin test (TST) and TB blood tests. A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to TB disease. Other tests, such as a chest x-ray and a sample of sputum, are needed to see whether the person has TB disease.
If a person is found to be infected with TB bacteria, other tests are needed to see if the person has latent TB infection or TB disease.
When TB bacteria become active (multiplying in the body) and the immune system can’t stop the bacteria from growing, this is called TB disease. TB disease will make a person sick. People with TB disease may spread the bacteria to people with whom they spend many hours.
It is very important that people who have TB disease are treated, finish the medicine, and take the drugs exactly as prescribed. If they stop taking the drugs too soon, they can become sick again; if they do not take the drugs correctly, the TB bacteria that are still alive may become resistant to those drugs. TB that is resistant to drugs is harder and more expensive to treat.
TB disease can be treated by taking several drugs for 6 to 9 months. There are 10 drugs currently approved by the U.S. Food and Drug Administration (FDA) for treating TB. Of the approved drugs, the first-line anti-TB agents that form the core of treatment regimens are: