What is Active Tuberculosis or TB?

Symptoms Begin With a Bad Cough, Chest Pain

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Tuberculosis, or “TB,” is an airborne contagious disease that can be fatal if left untreated. It is a disease that starts by infection in the lungs but can spread to other organs, including the kidney, brain, and spine. Still a leading killer worldwide, TB is less prevalent in the U.S. than it used to be, but infections have been on the rise in recent years.


When a person gets infected with TB, a person's immune system cells will usually wall off the infection and cause the TB bacteria to go into an inactive form that causes no symptoms and is not contagious.

If the immune system is weakened, however, the infection becomes active, causing symptoms and contagious disease. About 3% to 5% of people develop active TB within a year of receiving a positive diagnosis in a TB skin test or having evidence of a new infection. If the immune system becomes weakened for any reason, the infection can also become active, symptomatic and contagious.


Active TB begins with a bad cough (produces blood-tinged phlegm) that lasts 3 or more weeks and is accompanied by chest pain, fatigue, loss of appetite, weight loss, fever, chills and night sweating.


TB is treated with antibiotics. Treatment consists of 6 to 8 weeks of a combination of four drugs, followed by two medications for a total duration of 6 to 9 months. Treatment duration depends on the number of doses given per week. It is very important to follow doctor’s orders for treatment of TB, even after symptoms subside.

The full course of antibiotics is necessary for killing all of the TB bacteria. Failure to follow doctor’s orders can lead to ineffective treatment, longer illness, and antibiotic-resistant TB, whose treatment options are less effective and have more side effects than the preferred drugs.


With proper treatment, the prognosis for active TB is good.

Most cases of TB are treatable and curable, as long as medicines are taken according to doctor’s orders.


If you suspect that you have active TB, you can take a TB skin test. A health care worker will inject a few TB extracts under the skin on your forearm. An immune reaction to these extracts will result in swelling that can be detected within 2 to 3 days. Sometimes the test may be given too soon after exposure to TB for an immune response to develop -- usually 3 to 8 weeks following exposure. Testing for active TB is performed if the skin test is active or if active infection is suspected. These tests include a chest X-ray or CT scan and bacterial culture or microscopic examination of coughed up sputum (phlegm).

Preventing Transmission

Follow doctor’s orders for your prescribed antibiotics. Until your health care provider determines that you are no longer contagious (usually about 2 to 3 weeks after starting treatment, but may last up to 6 weeks), keep your distance from close contacts, including those at work or school. Remember to cough into a tissue, and discard the tissue in a sealed bag. If you receive a positive diagnosis of active TB, you will be instructed not to attend work or school until your doctor determines you are no longer contagious.

In many cases, patients with active TB are evaluated and treated in special hospital isolation rooms that are pressurized to limit exposure to others. After release from the hospital, public health officials will provide you with guidelines for returning to work or school. People with whom you have had contact, especially household or close contacts, should be tested for infection.


Centers for Disease Control. Division of Tuberculosis Elimination. https://www.cdc.gov/tb/?404;https://www.cdc.gov:443/tb/default

Mims CA, et al. Medical Microbiology. ©1993. Mosby-Year Book Europe Limited. London.

Salyers AA and Whitt DD. Bacterial Pathogenesis: A Molecular Approach. ©1994. American Society for Microbiology. Washington, D.C.

World Health Organization. Tuberculosis. http://www.who.int/tb/en/