Medically Reviewed By William C. Lloyd III, MD, FACS

What is tuberculosis?

Tuberculosis, or TB, is a serious bacterial infection which is very challenging to treat. It usually occurs in the lungs, but it can also affect other parts of the body, such as the brain, kidneys and bones. The bacterium Mycobacterium tuberculosis causes tuberculosis.

The WHO (World Health Organization) estimates that one-third of the world’s population is currently infected with tuberculosis. Nearly 1.5 million people worldwide die annually from the disease. Globally, 87% of cases occur in Africa, Southeast Asia, and the Western Pacific.

Tuberculosis is a contagious disease. It spreads when an infected person coughs or sneezes. This propels contaminated droplets into the air, where others can inhale the bacteria into their lungs.

People with healthy immune systems often do not get sick after infection with the tuberculosis bacteria. Their immune system is able to prevent the bacteria from growing and multiplying. So, they have no symptoms. Doctors call this latent tuberculosis. People with latent disease are not contagious and cannot spread it to others. However, anything that stresses the immune system, such as malnutrition or a chronic disease, can lower the body’s resistance. This allows the bacteria to become active and multiply.

When the tuberculosis organisms are able to grow and multiply, this is active tuberculosis. Active tuberculosis often affects the lungs. People with active disease appear sick and have symptoms, such as a chronic cough. Active tuberculosis is contagious.

Tuberculosis is usually treatable with antibiotics. However, some new strains of the bacteria are becoming resistant to many of them. This makes tuberculosis treatment harder in some cases.

Left untreated, active tuberculosis can spread in the body and result in serious damage to the lungs and other vital organs. Tuberculosis can eventually lead to death.

What are the different types of tuberculosis?

There are two types of tuberculosis that Mycobacterium tuberculosis (M. tuberculosis) can cause:

  • Latent or inactive tuberculosis occurs when a person becomes infected with tuberculosis, but the immune system is able to resist illness. People with latent disease do not have symptoms, do not feel sick, and are not contagious.

  • Active tuberculosis occurs when the body’s immune system cannot stop the bacteria from growing. It can develop within weeks after exposure to the bacteria. Active tuberculosis can also develop from a latent infection. This happens when something stresses or impairs the immune system, such as a chronic disease or HIV/AIDS. Lowering the body’s resistance allows the bacteria to become active and multiply.

A rare type, disseminated tuberculosis, occurs when the infection spreads beyond the lungs into other parts of the body, including the bones, brain, kidneys or spinal cord.

What are the symptoms of tuberculosis?

Mycobacterium tuberculosis (M. tuberculosis) mainly infects the lungs and causes a bad cough. The symptoms of tuberculosis can vary depending on the type or stage of tuberculosis.

Common active tuberculosis symptoms affect the lungs and include:

Serious symptoms that might indicate a life-threatening condition

Active tuberculosis can spread outside the lungs to other organs and areas of the body, such as the brain, kidneys, spinal cord, lymph nodes, and bones. This is disseminated tuberculosis. It is rare in the United States.

Seek prompt medical care if you have swollen lymph nodes or pain, swelling, or limited movement of your joints. Seek immediate medical care (call 911) for the following symptoms that may indicate a serious problem with the lungs or other organs and tissues:

What causes tuberculosis?

Tuberculosis is a bacterial infection of the lungs. The bacterium Mycobacterium tuberculosis (M. tuberculosis) causes the infection. It is a contagious disease that spreads through microscopic droplets. Infected people release these droplets when they cough, sneeze, spit, speak, laugh or sing.

Tuberculosis is not easy to catch. People usually get the infection from a household member or close contact. People are no longer contagious once they have completed two weeks of treatment.

What are the risk factors for tuberculosis?

A number of factors increase your risk of becoming infected with Mycobacterium tuberculosis and developing active disease including:

  • Close contact with a person with active tuberculosis, or working in a healthcare setting or with high-risk populations

  • Diabetes, kidney disease, malnutrition or being underweight

  • Exposure to areas that have high rates of tuberculosis, such as Southeast Asia and Africa

  • Homelessness and lack of medical care

  • Immunosuppression from HIV/AIDS and other conditions or immune-suppressing or antirejection drugs, including corticosteroids

  • IV drug abuse

  • Living in crowded conditions, such as in a prison or nursing home

How do you prevent tuberculosis?

Not all people who are at risk or exposed to tuberculosis will develop the disease. You can lower your risk of contracting, spreading or developing tuberculosis disease by:

  • Completing the screening skin test and diagnostic tests for tuberculosis as recommended by your healthcare provider or employer

  • Completing your medication treatment for latent infection or active tuberculosis exactly as directed

  • Following your employer’s guidelines for wearing a mask and washing your hands frequently if you work with a high-risk population

  • Obtaining the BCG tuberculosis vaccine if you have significant risk factors for infection and your doctor recommends it

  • Using good hygiene practices, such as washing your hands frequently and covering your mouth with a tissue when you cough or sneeze

If you have active disease, stay home for the first two weeks of treatment. Quarantine yourself from others in your home. Wear a mask if you must be around others. Finally, ventilate the room where you are staying. Open the windows, if possible, and use a fan to blow air out of the room to the outside.

How do doctors diagnose tuberculosis?

To diagnose tuberculosis, your doctor will take a medical history, perform an exam, and order testing. Questions your doctor may ask include:

  • What symptoms are you experiencing and when did they start?

  • Have you been around or lived with anyone with active tuberculosis?

  • Were you born in another country or have you recently traveled outside the United States?

  • Have you had the BCG tuberculosis vaccine?

  • Have you had a blood test for tuberculosis or skin tuberculosis test?

  • Have you ever had treatment for tuberculosis?

  • Have you been diagnosed with any other medical conditions that affect your immune system, such as HIV/AIDS?

  • Do you drink alcohol or use illicit drugs?

  • What do you do for a living?

During the exam, your doctor will check for signs of infection. This will include feeling your lymph nodes and listening to your lungs.

Tests to diagnose tuberculosis

The most common test for diagnosing tuberculosis is a skin test. It involves pricking your skin to inject tuberculin—a protein from the bacterium—into the outer layer of skin. Your doctor checks the area in 2 to 3 days to look for a reaction. When redness and swelling reaches a certain size, it indicates exposure to tuberculosis. Another name for this test is a PPD (purified protein derivative) test.

There are limitations to the skin test. It can give false results and show a reaction in people who have had the vaccine. So, doctors may confirm results with a blood test or use a blood test instead. Other confirmatory tests include:

  • Imaging exams, including a chest X-ray or CT (computed tomography) scan, to examine your lungs

  • Sputum test to look for tuberculosis organisms under the microscope and bacterial cultures to test for drug resistance

How do you treat tuberculosis?

Tuberculosis treatment begins with getting regular medical care throughout your life. Regular medical care allows your doctor to best evaluate your risk of becoming infected with the bacteria and developing the disease. Your doctor can promptly order screening and diagnostic testing as needed. These measures greatly increase the chances of diagnosing and treating tuberculosis in its earliest and most curable stage.

Tuberculosis is treatable. Prompt diagnosis and treatment can reduce the risk of developing serious complications, such as meningitis. You can help cure tuberculosis and eliminate its transmission by consistently following the treatment plan your doctor prescribes.

Treatment of latent tuberculosis

People with latent tuberculosis have fewer of the bacteria in their bodies compared to people with active disease. This makes the treatment easier. Treatment includes:

  • Isoniazid (INH), an antibiotic you take for at least nine months to kill all of the latent tuberculosis bacteria in the body

  • Rest and good nutrition, including treating nutritional deficiencies

Treatment of active tuberculosis

Doctors treat people with active tuberculosis with the following regimen:

  • Combination of several antibiotics (isoniazid, rifampin, ethambutol, and pyrazinamide) for 6 to 12 months. Drug-resistant tuberculosis may require additional or different drugs.

  • Direct observation of the patient taking the medication as directed, for individuals who are at risk of not adhering to their treatment plan

  • Rest and good nutrition, including treating nutritional deficiencies

What are the potential complications of tuberculosis?

Complications of untreated tuberculosis can be serious and life-threatening. You can help minimize the risk of serious complications by following the treatment plan you and your doctor design specifically for you.

Complications of tuberculosis include:

  • Adverse effects of treatment

  • Antibiotic resistance

  • Arthritis

  • Disseminated tuberculosis (tuberculosis that has spread beyond the lungs to other organs)

  • Lung and other organ damage

  • Mediastinitis (inflammation inside the mid-chest area)

  • Meningitis (infection and inflammation of the meninges, the membranes that cover the brain and spinal cord)

  • Pleural effusion (a buildup of fluid around the lungs)

  • Scrofula (tuberculosis infection of the lymph nodes)

Does tuberculosis shorten life expectancy?

Left untreated, tuberculosis can be fatal. However, with proper treatment, it is almost always curable. While deaths from tuberculosis are rare in the United States, it is still a top 10 killer worldwide.

Was this helpful?
  1. Tuberculosis (TB). Johns Hopkins University.
  2. Domino FJ (Ed.) Five Minute Clinical Consult, 27th ed. Philadelphia: Wolters Kluwer, 2019.
  3. Kellerman RD, Raker DP (Eds.) Conn’s Current Therapy, 72d ed. Philadelphia: Elsevier, 2020.
  4. Tuberculosis. Mayo Foundation for Medical Education and Research.
  5. Tuberculosis Facts. Centers for Disease Control and Prevention.
  6. Tuberculosis. MedlinePlus, National Library of Medicine, National Institutes of Health.
  7. Tuberculosis. World Health Organization.
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Oct 7
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