Tuberculosis

Written by Rachel Nall | Published on September 27, 2013
Medically Reviewed by George Krucik, MD, MBA on September 27, 2013

What Is Tuberculosis?

Tuberculosis (TB) is a highly infectious disease that primarily affects the lungs. It can also affect other organs. TB was once called “consumption.” It is the world’s second-most fatal infectious agent, after HIV/AIDS (WHO, 2013). TB is most common in developing countries, but people in the United States are diagnosed with the condition each year.

Tuberculosis is usually both preventable and curable under the right conditions.

What Causes Tuberculosis?

The mycobacterium tuberculosis bacterium causes TB. But there are a variety of TB strains. Some strains are resistant to medication. 

Bacteria are transmitted by air. They can be transmitted when a person sneezes, coughs, speaks, or sings. A nearby person can then inhale the TB bacteria.

People with strong immune systems may not experience TB symptoms, even though they carry the bacteria. This is known as latent or inactive TB. Inactive TB is not contagious. Active TB, however, can make you and other people sick.

Who Is at Risk for Tuberculosis?

An estimated 95 percent of all diagnosed TB cases are in developing countries (WHO, 2013). The condition chiefly affects young adults.

People who use tobacco or are long-term drug or alcohol abusers are more likely to get TB. People who have been diagnosed with HIV/AIDS or who suffer from malnourishment are also at greater risk. Diabetes, end-stage kidney disease, and certain cancers are other risk factors.

Some medications can also put a person at risk. These include medications that help prevent organ transplant rejection. Other medications that increase risk include those taken by patients with cancer, rheumatoid arthritis, Crohn’s disease, and psoriasis

Travel to regions where TB rates are high also carries the risk of infection. These include:

  • sub-Saharan Africa
  • India
  • Mexico
  • China
  • Parts of the former Soviet Union
  • Islands of Southeast Asia
  • Micronesia

In the United States, some low-income groups have limited access to resources for diagnosis and treatment. This can place them at greater risk of TB infection (Mayo Clinic, 2013).

What Are the Symptoms of Tuberculosis?

Some people carry the TB bacteria but do not experience symptoms. This condition is known as latent TB. Latent TB can develop into active TB.

Active TB causes many symptoms. Many are related to the respiratory system, including coughing up blood or sputum. Patients may experience a cough that lasts for over three weeks. They may also experience pain with coughing or even breathing normally, especially in the chest.

Other possible symptoms include unexplained fatigue, fever, night sweats, appetite loss, and weight loss.

While TB usually affects the lungs, it can also affect other organs, such as the kidneys, spine or brain. For example, tuberculosis of the kidneys may cause blood in the urine.

How Is Tuberculosis Diagnosed?

Doctors can use TB skin tests and blood tests to determine whether a person is carrying the TB bacteria. A TB skin test involves injecting 0.1 mL of a purified protein derivative of TB into the skin.

After two to three days, the patient returns to the doctor’s office. If the area around the injection is raised, the patient may be TB-positive. However, this test is not perfect. Some people do not respond to the TB test even if they have TB. People who have recently received the TB vaccine may test positive but not have TB.

A blood test is sometimes recommended to determine whether a patient has latent or active TB. These tests may not be available in all areas.

Other diagnostic tests include a chest X-ray, which checks for small spots in the lungs. These spots are a sign of TB infection and indicate that the body is trying to isolate TB bacteria. A physician may also order tests on sputum or mucus extracted from deep inside the lungs to check for the bacteria.

How Is Tuberculosis Treated?

Although most bacterial infections are treated with antibiotics over the course of a week or two, TB is different. Patients diagnosed with TB take one or more medications for six to nine months. The full treatment course must be taken, otherwise it is highly likely TB could come back. If TB does recur, it may be resistant to previous medications taken.

Because some TB strains are resistant to certain drug types, a doctor may prescribe multiple medications, including:

  • isoniazid
  • ethambutol (Myambutol)
  • pyrazinamide
  • rifampin (Rifadin, Rimactane)

High-dose antibiotics can harm the liver. Patients should be aware of liver-injury symptoms, such as:

  • appetite loss
  • dark urine
  • fever lasting longer than three days
  • unexplained nausea and/or vomiting
  • jaundice (yellowing of the skin)

Notify your doctor immediately if you experience these symptoms.

What Is the Outlook for Tuberculosis?

The outlook for TB patients depends on their overall health and on whether the TB responds to intervention. For example, if a person with TB has HIV/AIDS, the prognosis is poor because HIV/AIDS weakens the body’s ability to fight off the TB infection. An estimated 25 percent of all HIV/AIDS deaths are TB-related (WHO, 2013).

An estimated 8.4 million people were ill with active TB in 2011; 1.4 million of these people died from TB (WHO, 2013). But rates for TB cases are decreasing on a yearly basis. Early diagnosis and treatment, including a full course of antibiotics, offer the best chance for curing TB.

How Can Tuberculosis Be Prevented?

Most people in high-risk regions receive TB vaccinations as children. The vaccine is called Bacillus Calmette-Guerin, or BCG. This vaccine does not protect against all TB strains. It is not commonly given in the United States.

Having the TB bacteria does not guarantee symptoms of active TB. A doctor can prescribe preventive antibiotics to keep active TB from developing. A commonly prescribed medication is isoniazid (INH). Patients must take this medication for six to nine months to fully remove the bacteria.

Patients who have been diagnosed with TB should avoid crowds until the condition is no longer contagious. People with TB can infect between 10 and 15 people per year if precautions are not taken and treatment is not started (WHO, 2013). Patients can also wear a special surgical mask, known as a respirator, which keeps TB particles from spreading through the air. However, a person with active TB should avoid contact with others until finishing the first three to four weeks of treatment.

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