Tuberculosis (TB) is an infectious disease that mostly affects the lungs, but can also affect body parts like the spine, brain or kidneys. Everyone who is infected does not get sick. If you do get sick, you need treatment.
About 33 percent of the world's population, nearly 2.5 billion people, is infected with TB. Although TB was once the leading cause of death in the United States, the number of cases fell rapidly in the 1940s and 1950s after treatments were found.
According to statistics from the Centers for Disease Control (CDC), there were 9,272 tuberculosis cases reported in the United States in 2016. For TB, there is a national incidence rate of 2.9 cases per 100,000 people.
TB is caused by the bacterium Mycobacterium tuberculosis. The germs are spread through the air and usually infect the lungs, but can also infect other parts of the body. Although TB is infectious, it does not spread easily. You usually have to spend a lot of time in contact with someone who is contagious in order to catch it.
TB can be spread when a person with active TB disease releases germs into the air through coughing, sneezing, talking, singing, or even laughing. Only people with an active pulmonary infection are contagious. Most people who breathe in TB bacteria are able to fight the bacteria and stop it from growing. The bacterium becomes inactive in these individuals, and is referred to as a latent TB infection. Approximately 10 percent of the US population has latent infection.
Although the bacteria are inactive, they still remain alive in the body, and can become active later. Some people can have a latent TB infection for a lifetime, without it ever becoming active and developing into TB disease. However, TB can become active if the immune system becomes weakened and cannot stop the bacteria from growing. This is when the latent TB infection becomes TB disease.
People with inactive TB do not exhibit symptoms. However, they may have a positive skin reaction test.
Those with TB disease can show any of the following symptoms:
There are two kinds of screening tests for TB: the Mantoux tuberculin skin test (TST) and the blood test, called the interferon gamma release assay (IGRA).
For the TST, a healthcare provider will inject a small amount of a substance called purified protein derivative (PPD) under the skin of the forearm. After 2-3 days, the person must go back to the healthcare provider, who will look at the injection site. If the person has a TB infection, there will be a reddish lump.
For the IGRA, a healthcare provider will draw blood and send the sample to the lab.
Further tests to determine if an infection is active or if lungs are infected include:
You should consider a TB screening test if:
Others who are at risk for TB include:
The incidence rates for minority groups in the United States are higher than the incidence rates for whites.
Yes, TB can be cured, even in people with HIV infection. Drugs used to treat TB infection and disease include isoniazid (Hyzyd®), rifampin (Rifadin®), ethambutol (Myambutol®), pyrazinamide (Zinamide®), and a combination of isoniazid and rifapentine.
You must take all of the medication your doctor tells you to, or else not all of the bacteria will be killed. You will have to take these medications for as long as you are told—sometimes up to 9 months.
Yes. You usually have to be in contact with someone with active TB for a long time before becoming infected. The most important measure to prevent the transmission of TB in the hospital is to have proper ventilation and/or proper personal protective equipment (respirator).
Some countries (but not the United States) use a TB vaccine called bacillus Calmette-Guerin (BCG). The vaccine has been shown to work better in children than in adults. It may also make skin tests for TB less accurate.
CDC Hotline: 1.800-CDC-INFO (1.800.232.4636)
© Copyright 1995-2020 The Cleveland Clinic Foundation. All rights reserved.
This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: 11/09/2018