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What Is Tuberculosis?

Tuberculosis is an infectious disease caused by a type of bacteria called Mycobacterium tuberculosis. Tuberculosis (often called "TB") mainly infects the lungs, but can affect other organs.

Tuberculosis (too-bur-kyuh-LOW-sis) was one of the worst diseases of the 19th century. It became much rarer as living conditions and medical care got better in the United States. But it's making a comeback today, particularly among the homeless, those in prison, and people whose immune systems are weakened (for instance, from HIV infection).

Is Tuberculosis Contagious?

Yes. When someone with untreated TB coughs or sneezes, it sends droplets with the bacteria into the air. Inhaling these infected droplets is the usual way a person gets TB.

But not everyone who inhales infected droplets will get sick. That's why doctors categorize TB as either:

  • latent TB infection: This is when people have the M. tuberculosis bacteria in their bodies, but they don't feel sick or have symptoms. They also cannot pass TB to others.
  • TB disease: This is when people with M. tuberculosis bacteria become sick and have symptoms. Sometimes it can happen if a latent TB infection was not treated. They can spread TB to others.

What Are the Signs & Symptoms of Tuberculosis?

Someone with TB disease might have these symptoms:

  • unexplained weight loss
  • loss of appetite
  • night sweats
  • fever or chills
  • tiredness
  • coughing for 3 weeks or longer (and might cough up blood)
  • chest pain

How Is Tuberculosis Diagnosed?

A latent tuberculosis infection causes no signs or symptoms, and a chest X-ray won't show any signs of infection. Doctors can diagnose both latent TB infections and TB disease by doing a:

  • Tuberculin skin test (TST): This is how doctors usually test kids for TB. It's done in two steps. First, the health care provider injects a small amount of fluid (called tuberculin) into the skin on the lower part of the arm. Then, the person returns 48–72 hours later, when the provider checks the skin for a reaction. A raised, hard area or swelling means the person has TB bacteria in the body.
  • Blood test: The health care provider will take a blood sample to be checked in a lab for TB bacteria. This option doesn't need a second step.

Someone with a positive tuberculin test (PPD) will need more testing to see whether they have a latent TB infection or TB disease.

Who Should Get Tested for TB?

Health experts recommend TB testing for people at higher risk for TB disease, such as those who:

  • have symptoms of TB disease
  • were around someone with TB disease
  • have HIV or another condition that weakens the immune system
  • use illegal drugs
  • live in areas where the disease is common (including some countries in Asia, Latin America, Eastern Europe, and Africa)
  • live or work in settings where TB disease is more common (such as homeless shelters and prisons)

How Is Tuberculosis Treated?

Most people with tuberculosis don't need treatment in a hospital and can be cared for at home. Doctors usually treat TB with oral (taken by mouth) antibiotics. Killing all the TB bacteria takes time, though, so most people need to take medicine for 6–9 months. Sometimes doctors use a combination of bacteria-killing medicines to treat active TB.

It's important to take the antibiotics for as long as the doctor prescribed, even if someone feels better in a few weeks. That is the best way to kill the harmful bacteria. Stopping treatment too soon or skipping doses can give the remaining bacteria a chance to become resistant to the antibiotic. Drug resistance can lead to more dangerous types of tuberculosis that are harder to treat.

Doctors also might treat people with a latent infection and no symptoms. This is called preventive therapy. It kills the bacteria so they can't cause health problems later. The most common preventive therapy is a daily dose of an antibiotic called isoniazid taken for 6–9 months. Doctors also sometimes give isoniazid to people at risk for getting TB again.

Can Tuberculosis Be Prevented?

The prevention of TB depends on:

  • avoiding contact with people who have the active disease
  • using medicines as a preventive measure in high-risk cases
  • maintaining good living standards

To prevent the spread of germs that cause TB and other infections, encourage everyone in your family to:

  • Wash their hands well and often.
  • Sneeze or cough into a tissue or their elbow, not into their hands.
  • Use separate towels, drinking glasses, and eating utensils rather than sharing these items.

When Should I Call the Doctor?

Call the doctor if anyone in your family has:

  • had contact with someone who has tuberculosis
  • a long-lasting fever
  • night sweats
  • a long-lasting cough

Reviewed by: Aledie A. Navas, MD
Date Reviewed: Sep 18, 2019

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