What is TB?

Tuberculosis, or TB, is a bacterial infection that usually infects the lungs. Other organs, such as the kidneys, spine, or brain may also be involved. TB is primarily spread from person to person in an airborne manner, such as when an infected person coughs or sneezes. It can also cause an active infection after a period of not being active in someone who was exposed at an earlier time.

There is a difference between being infected with the TB bacterium and having active tuberculosis disease.

The following are the stages of TB:

1. Exposure. This happens when a person has been in contact with, or exposed to, another person who has TB. The exposed person will have a negative skin test, a normal chest X-ray, and no signs or symptoms of the disease.
2. Latent TB infection. This happens when a person has TB bacteria in his or her body, but does not have symptoms of the disease. The infected person's immune system walls off the TB organisms, and the TB remains inactive throughout life in most people who are infected. This person would have a positive skin test, but a normal chest X-ray.
3. TB disease. This describes the person who has signs and symptoms of an active infection. The person would have a positive skin test and a positive chest X-ray.

What causes TB?

The main TB bacterium is Mycobacterium tuberculosis (M. tuberculosis). Many people infected with this bacterium never develop active TB. They remain in the latent (inactive) TB stage. However, in people with weak immune systems, especially those with HIV (human immunodeficiency virus), or those receiving medicines that suppress the immune system, TB organisms can overcome the body's defenses, multiply, and cause an active disease.

The TB bacterium is spread through the air when an infected person coughs, sneezes, speaks, sings, or laughs. It’s not likely to be spread through personal items, such as clothing, bedding, a drinking glass, eating utensils, a handshake, a toilet, or other items that a person with TB has touched. Good ventilation is the most important measure to prevent the transmission of TB.

Who is at risk for TB?

TB affects people of all ages, races and income levels. Those at higher risk include the following:

• People who live or work with others who have TB
• Those who can’t access health care
• Homeless people
• People from other countries where TB is prevalent
• People in group settings, such as nursing homes
• People who abuse alcohol
• People who use intravenous drugs
• People with weak immune systems
• The elderly
• Healthcare workers who come in contact with high-risk populations

What are the symptoms of TB?

The following are the most common symptoms of active TB. However, each person may experience symptoms differently:

• Cough that lasts 3 weeks or longer
• Chest pain
• Fatigue
• Loss of appetite
• Unintended weight loss
• Poor growth in children
• Fever
• Coughing blood or sputum
• Chills or night sweats

The symptoms of TB may look like other lung conditions or medical problems. Talk with a healthcare provider for a diagnosis.

How is TB diagnosed?

TB can be diagnosed in multiple ways, depending on the stage of infection or disease. Individuals who have an asymptomatic (showing no symptoms), non-infectious form of TB infection (called latent TB infection, or LTBI) are screened for TB using a skin test or blood test.

• The skin test, called Mantoux tuberculin skin test (or TST) can be used to detect TB in all persons, including children under the age of 5. TST involves injection of a small, premeasured amount of purified protein derivative (or PPD) solution on the inside of the forearm. After 48-72 hours, a healthcare worker examines the site of injection for a reaction and to determine if the test is positive or negative. This is the only skin test for diagnosing TB that is approved by the U.S. Food and Drug Administration (FDA).
• The blood test, called Interferon Gamma Release Assay (or IGRA), involves a blood draw and lab testing to measure TB immune response. The FDA has approved two blood tests for detecting TB in persons over 5 years of age: QuantiFERON-TB Gold Plus (or QFT-Plus) and T-SPOT.TB test (or T-Spot). This is the preferred test for persons who have been vaccinated with the bacille Calmette-Guerin (BCG) tuberculosis vaccine.

Individuals who are infected with the active form of TB often have symptoms and are infectious to others. Persons being evaluated for active TB require specialized testing to confirm diagnosis. TB can be diagnosed using sputum tests including smear-microscopy, nucleic acid amplification tests, and culture, and with chest X-rays and tests that detect the presence of Mycobacterium tuberculosis, the bacterium that causes TB. 

How is TB treated?

Your healthcare provider will figure out the best treatment for you based on:

• How old you are
• Your overall health and past health
• How sick you are
• How well you can handle specific medicines, procedures, or therapies
• How long the condition is expected to last
• Your opinion or preference

Treatment may include:

• Short-term hospitalization
• For latent TB which is newly diagnosed: Usually a 6 to 12 month course of antibiotic called isoniazid will be given to kill off the TB organisms in the body. Some people with latent TB may be treated with a shorter course of 2 antibiotics for only 3 months.
• For active TB: Your healthcare provider may prescribe 3 or more antibiotics in combination for 6 to 9 months or longer. Examples include: isoniazid, rifampin, pyrazinamide, and ethambutol. People usually begin to improve within a few weeks of the start of treatment. After several weeks of treatment with the correct medicines, the person is usually no longer contagious, if treatment is carried through to the end, as prescribed by a healthcare provider.

What are the complications of TB?

If TB is not treated early or if treatment isn’t followed, permanent lung damage can result.

Can TB be prevented?

If you will be spending time with a person or people with active TB, wear a face mask and try not to stay in a small enclosed space with poor ventilation. People who work in situations where there is a high risk for encountering people infected with TB, such as healthcare workers, should be tested for TB on a routine basis. In countries outside the U.S. where TB is more common, a childhood vaccine is often given.

When should I call my healthcare provider?

If your symptoms get worse or you get new symptoms, let your healthcare provider know.

Key points about TB

• Tuberculosis is a bacterial infection that usually infects the lungs.
• It may also affect the kidneys, spine, and brain.
• Being infected with the TB bacterium is not the same as having active tuberculosis disease.
• There are 3 stages of TB—exposure, latent, and active disease.
• A TB skin test or a TB blood test can diagnose the disease.
• Treatment exactly as recommended is necessary to cure the disease and prevent its spread to other people.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your provider tells you.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your provider if you have questions.

Review date: Jan. 31, 2025.