Tuberculosis (too-ber-kyoo-LO-sis) is a bacterial infection that primarily attacks the lungs but can spread to other parts of the body.
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Directly observed therapy (DOT)
Tuberculin skin test
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.
HIV and TB: A Lethal Combination
One of the reasons for the surge in TB cases in the 1980s was the rapid increase in the number of HIV cases. Because HIV/AIDS weakens the immune system, patients who have HIV/AIDS are at high risk for contracting TB when the germ first is breathed in. Approximately 11 million people around the globe are infected with both HIV and TB. TB is more likely to spread to other areas of the body in people with HIV, and multidrug-resistant (MDR) TB is much more dangerous in these patients. TB infection in patients who have HIV/AIDS can be cured if found and treated early.
* kidneys are the pair of organs that filter blood and remove waste products and excess water from the body in the form of urine.
* gastrointestinal (gas-tro-in-TES-tih-nuhl) means having to do with the organs of the digestive system, the system that processes food. It includes the stomach, intestines, and other organs involved in digestion, including the liver and pancreas.
* AIDS, or acquired immunodeficiency (ih-myoo-no-dih-FIH-shen-see) syndrome, is an infection that severely weakens the immune system: it is caused by the human immunodeficiency virus (HIV).
* chronic (KRAH-nik) means continuing for a long period of time.
* intravenous (in-tra-VEE-nus) means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.
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
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.
* mucus (MYOO-kus) is a thick, slippery substance that lines the insides of many body parts.
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
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.
Multidrug-resistant tuberculosis (MDR TB) occurs when TB patients stop taking their prescribed medications or do not take them as directed. Patients often stop taking the drugs when they begin to feel better or to avoid side effects. However, TB bacteria can survive inside the body for several months during treatment and are ready to spring back into activity when the medication disappears.
Symptoms return with a vengeance, and infected people become highly contagious again, putting those close to them at risk. In MDR TB, germs become stronger than the antibiotics, making the drugs less effective. Patients with MDR TB need special medications, but they may not work as well. In addition, patients can spread this highly dangerous form of the disease to others.
One way to fight this problem is through directly observed therapy (DOT). In DOT, patients must take their medications regularly in the presence of a health professional. Home visits by health professionals to supervise the taking of medications or free transportation and meals often are provided to encourage patients to take part in this type of program.
* sputum (SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.
* vaccine (vak-SEEN) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that ca n result if a person is exposed to the germ itself. Use of vaccines for this purpose is called immunization.
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
American Lung Association, 61 Broadway, 6th Floor, New York, NY 10006.
The American Lung Association offers information about tuberculosis and
other diseases that affect the lungs at its website.
National Institute of Allergy and Infectious Diseases (NIAID), Building
31, Room 7A-50, 31 Center Drive MSC 2520, Bethesda, MD 20892. The NIAID,
part of the National Institutes of Health, posts information about
tuberculosis at its website.
U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton
Road, Atlanta, GA 30333. The CDC is the U.S. government authority for
information about infectious and other diseases. It provides information
about tuberculosis at its website.
World Health Organization (W'HO), Avenue Appia 20, 1211 Geneva
27, Switzerland. WHO posts information about tuberculosis and tracks TB
cases worldwide on its website.