Tuberculosis

Tuberculosis (too-ber-kyoo-LO-sis) is a bacterial infection that primarily attacks the lungs but can spread to other parts of the body.

What Is Tuberculosis?

A germ known as Mycobacterium (my-ko-bak-TEER-e-um) tuberculosis causes tuberculosis (TB). Being infected with the bacterium and actually having the disease tuberculosis are very different. When most people breathe in M. tuberculosis bacteria, the immune system quickly seals off the invading bacteria in the lungs and protects the body from illness. These people are said to have latent, or inactive, TB (also called primary infection): their bodies carry the germs, but they have no symptoms and are not contagious. However, latent TB germs sometimes escape the immune system's barriers and cause disease.

When a person's immune system is no longer able to contain the bacteria, or if latent TB activates for other reasons, tuberculosis disease, or active TB, develops (also called secondary infection). Patients may feel sick quickly or develop symptoms gradually over weeks or months, and they may be highly contagious until treated. If TB travels through the blood to invade organs outside the lungs, it is known as disseminated TB. Many organs and bones, including the brain, pericardium (sac surrounding the heart), kidneys ^* , gastrointestinal ^* tract, and spine, can become involved and be damaged by the infection.

Is TB Common?

TB is one of the most common causes of death due to infection in the world. About 2 million people around the world die from TB each year. In the nineteenth century, TB was a major cause of death, especially among young children. Drugs to treat the disease were first developed in the 1940s, and they dramatically lowered the number of TB cases over the next few decades. Unfortunately, TB began to resurface in the 1980s, but the number of cases has been declining in recent years. Between 10 and 15 million Americans are believed to have latent TB.

There are several reasons why TB made a comeback:

• HIV/AIDS ^* has weakened the immune systems of many people, increasing their likelihood of contracting TB.
• Increased numbers of malnourished, poor, or homeless people live in crowded, unclean conditions and are vulnerable to infection.
• TB bacteria become more resistant to medications when patients do not take the drugs as prescribed. Multidrug-resistant (MDR) TB is difficult to treat and spreads easily.
• Immigration to the United States from countries with high rates of TB has increased.

TB can affect anyone, but it is most common among immigrants from countries with high levels of TB and people whose immune systems are weak because of chronic ^* illness, medications that affect the immune system, infancy, old age, poor nutrition, unclean or crowded living areas (including prisons), alcoholism, or intravenous ^* (IV) drug use.

In the twenty-first century, the number of TB cases is falling once again in the United States thanks to effective public health measures, including

finding contacts of anyone known to have TB so that they may be treated as well, and directly observing that patients take medication as prescribed.

How Is TB Spread?

Active TB involving the lungs is highly contagious if untreated. Like the flu, TB is spread through the air. When a person with active TB sneezes, coughs, or talks closely to others, bacteria are passed through tiny drops of fluid from the mouth and nose that are unknowingly breathed in by others. Spending lots of time in close quarters with a person who has untreated active TB is the most common way to become infected. A brief encounter with an infected person usually does not spread TB. Touching an infected person or his or her belongings does not put a person at risk for TB. Within a few weeks of the start of effective treatment, patients are no longer contagious.

What Are the Signs and Symptoms of TB?

People with latent TB have no symptoms, but they need to be aware of signs of active TB. Active TB may begin with mild symptoms like those of the flu but quickly worsens. Possible symptoms include:

• cough that lasts a long time
• coughing up blood or lots of mucus ^*
• chest pain
• loss of appetite and weight loss
• weakness and exhaustion
• fever and chills
• night sweats

If TB spreads to other parts of the body, additional serious symptoms may occur, depending on the organs involved.

How Do Doctors Diagnose and Treat TB?

TB infection is detected through a skin test known as the Mantoux test or PPD (purified protein derivative) test. A tiny amount of tuberculin (too-BER-kyoo-lin) substance, a protein taken from M. tuberculosis, is injected into the skin of an arm. A few days later a health professional will check to see if a bump has formed at the site of the injection. If the bump is wider than a certain size (for most people, 10 to 15 millimeters or a half inch), the patient most likely has been infected by TB bacteria; this is known as a positive skin test.

Next, a doctor will determine if the patient has active TB through a physical exam and by asking about symptoms and people the patient has had close contact with recently. The doctor may hear "crackles" when listening to the lungs with a stethoscope if a person has active TB. A chest X ray will be done, and samples of sputum ^* , blood, and urine may be tested. It can take weeks to confirm a diagnosis, although treatment can begin based on the skin test results and the person's symptoms.

Both latent and active TB can be cured if patients closely follow their doctors' orders. Antibiotics must be taken by mouth every day for 6 months to 1 year. Hospitalization and isolation may be required in the early stages of active disease for people who are highly contagious or who have severe symptoms. Patients must continue to take medications even if they begin to feel better. If they do not, the germs that are still in the body can cause symptoms to return and drugs to stop working properly due to the development of MDR TB.

Once treatment begins, TB symptoms disappear within a few weeks. People with TB can lead normal, active lives while taking their medications over the course of several months.

What Are Some Complications of TB?

Complications of TB include:

• side effects of the drugs used to treat TB, which range from mild to severe
• lung damage and difficulty breathing
• damage to other organs from disseminated TB
• development of MDR TB
• other bacterial infections
• death

Can TB Be Prevented?

The Centers for Disease Control and Prevention recommends that people at high risk for TB (such as those with HIV infection or immigrants from areas with high rates of TB) get a skin test yearly so that treatment can begin immediately if they are found to have TB.

A TB vaccine ^* is given to infants and toddlers in countries with high levels of the disease. The vaccine is not commonly used in the United States because it does not always work and it may cause a positive skin test, making it more difficult to detect true TB infection.

Practical prevention tips include:

• avoiding close contact with people infected with TB until they are no longer contagious
• wearing a special type of facemask (called a respirator) that can prevent the spread of TB if close contact with someone who has TB is necessary