Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain. Not everyone infected with TB bacteria becomes sick. As a result, two TB-related conditions exist: latent TB infection (LTBI) and TB disease. If not treated properly, TB disease can be fatal.

How TB Spreads

TB is spread through the air when a person with active TB disease coughs or sneezes. People nearby can breathe in these bacteria and become infected. People with the highest risk are those who have prolonged or frequent contact with an infected individual, such as family members, friends or coworkers.

Someone with latent TB infection (LTBI) cannot spread it to others. 

Latent TB Infection and TB Disease

Not everyone infected with TB bacteria becomes sick.

People with a latent TB infection have TB bacteria in their body, but their immune system can fight off the infection. They do not feel sick and do not have symptoms of TB infection. They cannot spread the infection to others. People with a latent TB infection will usually test positive test for TB. 

Many people with latent TB infection will never develop TB disease. However, the bacteria can become active and cause TB disease. Sometimes, people with a latent TB infection will need treatment to prevent TB disease. There are several options available. Discuss with a health care provider to determine which plan is appropriate. Taking medicine as directed can prevent progression to TB disease.

People with TB disease have active bacteria in their body. They are usually sick and have symptoms of TB. They can spread the infection to others and require treatment for TB disease.

A Person with Latent TB Infection A Person with TB Disease
Has no symptoms Has symptoms that may include:
  • a bad cough that lasts 3 weeks or longer

  • pain in the chest

  • coughing up blood or sputum

  • weakness or fatigue

  • weight loss

  • no appetite

  • chills

  • fever

  • sweating at night

Does not feel sick Usually feels sick
Cannot spread TB bacteria to others May spread TB bacteria to others
Usually has a skin test or blood test result indicating TB infection Usually has a skin test or blood test result indicating TB infection
Has a normal chest x-ray and a negative sputum smear May have an abnormal chest x-ray, or positive sputum smear or culture
Needs treatment for latent TB infection to prevent active TB disease Needs treatment for active TB disease

Signs & Symptoms

Most people infected with the bacteria that cause TB never develop TB disease.

If TB disease does develop, symptoms can occur two to three months after infection or even years later.

Symptoms of TB disease depend on what part of the body is infected. Symptoms of TB disease include:

  • persistent coughing

  • fatigue

  • weight loss

  • fever

  • night sweats

Who is at Risk for TB?

While anyone can develop a TB infection, some people have a higher risk for developing TB disease. People with a high risk of developing an active TB infection include:

  • People with HIV infection

  • People who became infected with the TB bacteria during the last two years

  • Injection Drug users

  • People with weakened immune systems

  • Babies, young children, and the elderly

  • People who were not properly treated for TB in the past

TB and HIV

HIV is the strongest risk factor for people with a latent TB infection to develop TB disease. All people living with HIV should be tested for TB. An untreated latent TB infection can quickly progress into TB disease among people with HIV. Treatment is available for people with both HIV and TB.

Information for Travelers

Travelers who will be working in a health care setting where there are known TB patients should ask about procedures for preventing TB exposures.

Travelers who anticipate exposure to people with TB should have a TB skin or blood test before leaving the United States. If the test is negative, they should have a repeat test eight to 10 weeks after they return to the United States.

For additional information, consult with a travel clinic or with your health care professional about specific recommendations.

Learn more about preventing TB while traveling from the CDC

Additional Resources
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Tuberculosis: Get the Facts!
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What Parents Should Know about Tuberculosis
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