Tuberculosis (TB) is a contagious bacterial infection caused by Mycobacterium tuberculosis that primarily affects the lungs and is spread through the air from person to person by droplets. Infection occurs by inhaling these droplets after an infected person coughs, sneezes, speaks, sings, or laughs. Anyone can get tuberculosis, but risk increases with close or prolonged contact with a person with active TB disease or presence of a health problem that weakens the immune system. It is possible to be infected with tuberculosis more than once.
Nearly one-third of the world's population is infected with tuberculosis. In 2015, 10.4 million people worldwide became sick with TB disease. In the United States, 9,557 people became sick with TB disease with the highest rates among people with HIV and those born in countries were tuberculosis is common.
Tuberculosis can remain inactive in the body, a condition known as latent tuberculosis infection (LTBI). One is not sick or contagious with latent tuberculosis. However, without treatment about 5% to 10% of people with latent TB will develop active TB disease. With active TB disease the person becomes very sick, contagious and must be isolated. Students with active TB disease risk their grades and enrollment and may infect friends and classmates.
Symptoms of active tuberculosis disease include:
- Fever for several weeks (temperature over 100°F or 37.7°C)
- A bad cough that lasts 3 weeks or longer
- Chest pain
- Coughing up blood
- Unexplained weight loss and wasting
- Night sweats (soaking nightclothes and bedding and not related to room heat or blankets)
- Weakness and unusual tiredness
There are two tests for TB infection. The first is a blood test: interferon gamma release assay, for example QuantiFERON-TB Gold (QFT). Results are generally available within several days. The second method is the tuberculin skin test (TST) which requires a return visit for the reading in 48 to 72 hours. If either of these tests indicate TB infection, a chest x-ray is the next step for diagnosis.
To prevent TB, avoid contact with people who have active TB disease. Persons with active TB disease must be isolated and treated with specific antibiotics. Healthcare workers must follow TB control plans. Bacille Calmette-Guèrin vaccine (BCG) for tuberculosis is not used in the United States because it does not completely prevent TB. In countries where TB is common, BCG is often given to infants and children. History of BCG vaccine does not affect the blood test but may affect the skin test.
Latent tuberculosis infection can be treated by taking several months of antibiotics. During treatment, the health care provider monitors the patient’s health and response to the medications.
Active tuberculosis disease is also treated with antibiotics, based on the culture and sensitivity of the bacteria. Often, more than one drug is needed. Isolation from other people is required for several weeks until the patient is no longer contagious. Throughout the contagious time, the person with tuberculosis disease must not attend class, jobs or social events.
In both active and latent tuberculosis, it is very important to follow the medication schedules, complete all medications and stay in touch with the provider.
- “UpToDate” link on this web site