Causes and Symptoms (Magill’s Medical Guide, Sixth Edition)
Tuberculosis derives its name from the Latin word tubercle, which means “little lump.” Tubercles, or small nodules of diseased tissue, are often found in the lungs of infected individuals. In humans, bacteria that belong to the genus Mycobacterium cause tuberculosis. In the vast majority of cases, Mycobacterium tuberculosis, often referred to as the tuberculosis bacillus or the tubercle bacillus, is the responsible organism. Other species within the genus may also cause tuberculosis or tuberculosis-like diseases. For example, M. avium, a disease-causing organism, or pathogen, is found in birds and swine; it can cause a tuberculosis-like disease in humans. Before it was common to pasteurize milk, M. bovis, a pathogen found in cattle, was responsible for cases of human tuberculosis of the digestive tract. In most cases of tuberculosis in humans, the lungs are the major organs affected, but other tissues and organs such as the bones, skin, and digestive tract may also be sites of infection.
Poverty, overcrowding, unsanitary conditions, poor health, and poor nutrition provide ideal conditions for the spread of tuberculosis. It is found at a high frequency in the developing areas of the world, such as parts of Africa, Asia, and Oceania. Immigrants from these countries present a serious public health concern when they enter the United States and other countries. In the United...
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Treatment and Therapy (Magill’s Medical Guide, Sixth Edition)
On a global basis, close to ten million new cases of tuberculosis are diagnosed each year, and approximately three million deaths are attributable to this disease. Every minute, ten new people become infected with tuberculosis; of these, three will die from it. Since tuberculosis presents a serious public health concern, many countries have employed strategies to prevent its spread. Control of the spread of tuberculosis could decrease the numbers of new cases seen each year. Improvements in living conditions, sanitation, and general standards of living have, in the past, been associated with the decreased incidence of tuberculosis in populations. These goals cannot easily be met in impoverished regions of the world. The medical approaches designed to inhibit the further transmission of tuberculosis include vaccination, rapid diagnosis, and the development of effective drug treatments.
In the United States after the mid-twentieth century, measures were developed to diagnose tuberculosis and prevent its transmission. This program resulted in a marked decrease in death rates from tuberculosis. Total death rates declined dramatically until the mid-1980’s. Believing that the disease was one of the past, New York City officials dismantled the entire public tuberculosis health infrastructure of hospitals, sanatoriums, and diagnosis centers during the 1970’s. Only a decade later, the city was forced to rebuild that system...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Throughout the ages, tuberculosis has been a scourge of humankind. Human fossils, excavated from a Neolithic burial ground dated about six thousand years ago, show evidence of tuberculosis of the spine. Egyptian mummies from 1000 b.c.e. with signs of tuberculosis suggest that the disease was widespread in ancient Egypt. Symptoms of tuberculosis such as fever, excessive weight loss, night sweats, breathlessness, pain in the side and chest areas, and coughing up of sputum and blood are described in the writings of ancient Hindu, Greek, and Roman writers. The widespread nature of the disease appears in accounts from early European history, from the fifth to eighteenth centuries, which refer to a “touching” ceremony that was performed by English and French monarchs and believed to cure scrofula (tuberculosis of the lymph glands in the neck region).
One of the greatest causes of disease and death in the world, tuberculosis has been known by many names, including scrofula, phthisis, and consumption. In writings, it has been referred to as “the white plague” and “the captain of all the men of death.” During the nineteenth century, tuberculosis was widespread in Europe. The symptoms of tuberculosis were not thought to represent a disease but rather hallmarks of an especially sensitive personality—the ideal for an artist, musician, poet, or writer. At that time, it was somewhat fashionable to be pale and thin,...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
American Lung Association. http://www.lungusa.org. A group initially founded to fight tuberculosis, it now targets its efforts toward asthma, tobacco control, environmental health, and the global rise of tuberculosis. The Web site offers a comprehensive fact sheet about the disease, as well as resources for advocacy, research, and relevant news stories.
Daniel, Thomas M. Captain of Death: The Story of Tuberculosis. Rochester, N.Y.: University of Rochester Press, 1997. This book is written for nonprofessional readers. It is interesting and well researched.
Dormandy, Thomas. The White Death: A History of Tuberculosis. New York: New York University Press, 2000. Accessible scientific and sociological history are combined by Dormandy, a consulting pathologist in London, in this account of a tenacious disease that has claimed victims since ancient Egypt.
Gandy, Matthew, and Alimuddin Zumla, eds. Return of the White Plague: Global Poverty and the “New” Tuberculosis. New York: Verso, 2003. Examines the global rise of tuberculosis from a socioeconomic and medical perspective, arguing that the increase can be blamed on collapsing health care services, shifting patterns of poverty and inequality, the spread of HIV, and the emergence of virulent drug-resistant strains.
Levitzky, Michael G. Pulmonary Physiology. 7th ed. New York: McGraw-Hill Medical, 2007. A clinical...
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Tuberculosis (Encyclopedia of Medicine)
Tuberculosis (TB) is a potentially fatal contagious disease that can affect almost any part of the body but is mainly an infection of the lungs. It is caused by a bacterial microorganism, the tubercle bacillus or Mycobacterium tuberculosis. Although TB can be treated, cured, and can be prevented if persons at risk take certain drugs, scientists have never come close to wiping it out. Few diseases have caused so much distressing illness for centuries and claimed so many lives.
Tuberculosis was popularly known as consumption for a long time. Scientists know it as an infection caused by M. tuberculosis. In 1882, the microbiologist Robert Koch discovered the tubercle bacillus, at a time when one of every seven deaths in Europe was caused by TB. Because antibiotics were unknown, the only means of controlling the spread of infection was to isolate patients in private sanitoria or hospitals limited to patients with TB practice that continues to this day in many countries. The net effect of this pattern of treatment was to separate the study of tuberculosis from mainstream medicine. Entire organizations were set up to study not only the disease as it affected individual patients, but its impact on the society as a whole. At the turn of the twentieth...
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Tuberculosis (Encyclopedia of Children's Health)
Tuberculosis is a chronic, infectious disease that primarily attacks the lungs.
Tuberculosis (TB) is caused by a bacteria that primarily attacks the lungs. An individual may be "TB infected," meaning the bacteria are in the body but are in an inactive state, walled off behind scab-like structures that are the body's defense mechanism, or have "TB disease," when the bacteria actively spread throughout the body and can cause damage to the lungs or other organs. The severity of the attack depends on whether the bacteria spread from the lungs to other parts of the body. TB infection in the blood, the meninges (membranes around the brain and spinal cord), or the kidneys are the most serious. Children between the ages of six and 24 months are the most susceptible to meningitis; it is the chief cause of tuberculin death among children.
The bacteria that causes TB, Mycobacterium tuberculosis, is transmitted by droplets when an infected person coughs or sneezes. It is not spread through kissing or other physical contact. Children nearly always contract the disease from an infected adult.
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Tuberculosis (Encyclopedia of Alternative Medicine)
Tuberculosis (TB) is a contagious and potentially fatal disease that can affect almost any part of the body but manifests mainly as an infection of the lungs. It is caused by a bacterial microorganism, the tubercle bacillus or Mycobacterium tuberculosis. TB infection can either be acute and short-lived or chronic and long-term.
Although TB can be prevented, treated, and cured with proper treatment and medications, scientists have never been able to eliminate it entirely. The organism that causes tuberculosis, popularly known as consumption, was discovered in 1882. Because antibiotics were unknown, the only means of controlling the spread of infection was to isolate patients in private sanatoria or hospitals limited to patients with TB practice that continues to this day in many countries. TB spread very quickly and was a leading cause of death in Europe. At the turn of the twentieth century more than 80% of the people in the United States were infected before age 20, and tuberculosis was the single most common cause of death. Streptomycin was developed in the early 1940s and was the first antibiotic effective against the disease. The number of cases declined until the mid- to late-1980s, when overcrowding, homelessness, immigration, decline in public health inspections, decline in funding, and the...
(The entire section is 3361 words.)
Tuberculosis (Encyclopedia of Nursing & Allied Health)
Tuberculosis (TB) is a potentially fatal contagious disease that can affect almost any part of the body but is mainly an infection of the lungs. It is caused by a bacterial microorganism: the tubercle bacillus or Mycobacterium tuberculosis. Although TB can be treated and cured, and can be prevented if persons at risk take certain drugs, medical science has never succeeded in eradicating the disease. Few diseases have caused so much distressing illness for centuries and claimed so many lives.
Tuberculosis was popularly known as consumption for many years. Scientists now know that it is an infection caused by M. tuberculosis. In 1882, one of every seven deaths in Europe was caused by TB. In that year, the microbiologist Robert Koch discovered the tubercle bacillus. Because antibiotics were unknown, the only means of controlling the spread of infection was to isolate patients in private sanitariums or hospitals limited to treating persons with TB. In many countries, this practice continues to this day. The net effect of this approach to treatment was to separate the study of tuberculosis from mainstream medicine. Entire organizations were set up to study not only the disease as it affected individual persons, but also its impact on society as a whole. At the turn of the twentieth century, more than 80% of the population in the United States was infected with TB before age 20, and tuberculosis was the single most common cause of death. By 1938, there were more than 700 TB hospitals in the United States.
When the industrial revolution began in the late nineteenth century, tuberculosis spread much more widely in Europe. Later, the disease began to spread throughout the United States, primarily due to the population migration to large cities that made overcrowded housing so common. When streptomycin, the first antibiotic effective against M. tuberculosis, was discovered in the early 1940s, the infection began to come under control. Although other, more effective anti-tuberculosis drugs were developed in the following decades, the number of cases of TB in the United States began to rise again in the mid-1980s. In part, this upsurge was again a result of overcrowding and unsanitary conditions in poor areas of large cities, prisons, and homeless shelters. Infected visitors and immigrants to the United States also contributed to the resurgence of TB. An additional factor was the emergence of acquired immunodeficiency syndrome (AIDS). Persons with AIDS are much more likely to develop tuberculosis because of their weakened immune systems than are others in the general population. As of 2001, experts estimate that between 8 and 11 million new cases of TB are reported each year throughout the world. These are estimated to cause approximately 3 million deaths. This situation is worsening. The World Health Organization estimates that by 2020, there will be 1 billion TB cases worldwide and 35 million deaths each year.
THE ELDERLY. Tuberculosis is more common in elderly persons. More than one-fourth of the 19,855 cases of TB (7.4 cases per 100,000 population) reported in the United States in 1997 developed in people above the age of 65. Many elderly individuals developed the infection some years ago when the disease was more widespread. There are additional reasons for the vulnerability of older people. Those living in nursing homes and similar facilities are in close contact with others who may be infected. The aging process itself may weaken the body's immune system, which is then less able to successfully eliminate the tubercle bacillus. Finally, bacteria that have been dormant for some time in elderly persons may be reactivated and cause illness.
RACIAL AND ETHNIC GROUPS. TB also is more common among members of minority groups who may be likely to live under conditions that promote infection. As of 2001, approximately two-thirds of all cases of TB in the United States affect African Americans, Hispanics, Asians, and persons from the Pacific Islands. Another one-fourth of cases affect persons born outside the United States. The risk of TB has not diminished among members of these groups.
PERSONS WITH RELEVANT LIFESTYLE FACTORS. The high risk of TB in AIDS patients extends to those infected by human immunodeficiency virus (HIV) who have not yet developed clinical signs of AIDS. Alcoholics and intravenous drug abusers are also at increased risk of contracting tuberculosis. Until the economic and social factors that influence the spread of tubercular infection are addressed and eliminated, there is no real possibility of completely eliminating the disease.
Causes and symptoms
Tuberculosis is spread by droplet infection. This type of transmission means that when a TB patient exhales, coughs, or sneezes, tiny droplets of fluid containing tubercle bacilli are released into the air. This mist, often referred to as aerosol, can be taken into the nasal passages and lungs of a nearby susceptible person. Compared to some other infectious diseases, TB is not highly contagious. Only about one in three close contacts of a person with TB is likely to become infected. Fewer than 15% of more remote contacts are likely to become infected. As a rule, close, frequent, or prolonged contact is needed to spread the disease. Of course, if a severely infected patient emits huge numbers of bacilli, the chance of transmitting infection is much greater. Unlike many other infections, TB is not passed on by contact with a patient's clothing, bed linens, or dishes and cooking utensils. The most important exception is pregnancy. The fetus of an infected mother may contract TB by inhaling or swallowing bacilli that may be present in amniotic fluid.
Once inhaled, tubercle bacilli may reach the small breathing sacs in the lungs (alveoli), where they are taken up by cells called macrophages. The bacilli multiply within these cells and then spread through lymph vessels to nearby lymph nodes. Sometimes the bacilli move through blood vessels to distant organs. At this point they may either remain alive but inactive (quiescent), or they may cause active disease. Actual tissue damage is not caused directly by the tubercle bacillus, but by the reaction of a person's tissues to its presence. In a matter of weeks, the host develops an immune response to the bacillus. Cells attack the bacilli, permit the initial damage to heal, and permanently prevent future disease.
Exposure and infection does not always mean that active TB disease will develop. In fact, most people who are infected do not develop TB. At least nine out of ten people who harbor M. tuberculosis do not develop symptoms or physical evidence of active disease, and their x rays remain negative. They are not contagious. However, they do form a pool of infected people who may get sick at a later date and then pass their TB on to others. It is thought that more than 90% of active tuberculosis cases come from this pool. In the United States, this group numbers 10 to 15 million persons. Whether or not a particular infected person will become ill is impossible to predict with certainty. An estimated 5% of infected persons develop active cases of TB within 12-24 months of being infected. Another 5% heal initially, but after years or decades develop active tuberculosis either in the lungs or elsewhere in the body. This form of the disease is called reactivation TB, or post-primary disease. On rare occasions, a previously infected person gets sick again after a later exposure to the tubercle bacillus.
Pulmonary tuberculosis is TB that affects the lungs. Its initial symptoms are easily confused with those of other diseases. An infected person may at first feel vaguely unwell or develop a cough blamed on smoking or a cold. A small amount of light green or yellow sputum may be coughed up when the person gets up in the morning. In time, more sputum is produced that is streaked with blood. Persons with pulmonary TB do not run a high fever, but they often have a low-grade one. They may wake up in the night drenched with cold sweat when the fever breaks. A person often loses interest in food and may lose weight. Chest pain is sometimes present. If the infection allows air to escape from the lungs into the chest cavity (pneumothorax) or if fluid collects in the pleural space (pleural effusion), an affected person may have difficulty breathing. If a young adult develops a pleural effusion, the probability of tubercular infection being the cause is very high. TB bacilli may travel from the lungs to lymph nodes in the sides and back of the neck. Infection in these areas can break through the skin and discharge pus. Before the development of effective antibiotics, many patients became chronically ill with increasingly severe lung symptoms, lost a great deal of weight, and developed a wasted appearance. This out-come is uncommon todayt least where modern methods of treatment are available.
Although the lungs are the major site for damage caused by tuberculosis, many other organs and tissues in the body may be affected. The usual progression is for the disease to spread from the lungs to locations outside the lungs (extrapulmonary sites). In some cases, however, the first sign of disease appears outside the lungs. The many tissues or organs that tuberculosis may affect include:
- Bones. TB is particularly likely to attack the spine and the ends of the long bones. Children are especially prone to spinal tuberculosis. If not treated, the spinal bones (vertebrae) may collapse and cause paralysis in one or both legs.
- Kidneys. Along with bones, the kidneys are probably the most common site of extrapulmonary TB. There may, however, be few symptoms even though part of a kidney is destroyed. TB may spread to the bladder. In men, it may spread to the prostate gland and nearby structures.
- Female reproductive organs. The ovaries in women may become infected as TB can spread from them to the peritoneum, which is the membrane lining the abdominal cavity.
- Abdominal cavity. Tuberculous peritonitis may cause pain ranging from the vague discomfort of stomach cramps to intense pain that may mimic the symptoms of appendicitis.
- Joints. Tubercular infection of joints causes a form of arthritis that most often affects the hips and knees. The wrist, hand, and elbow joints also may become painful and inflamed.
- Meninges. The meninges are tissues that cover the brain and the spinal cord. Infection of the meninges by TB bacillus causes tuberculous meningitis, a condition that is most common in young children but is especially dangerous in the elderly. Affected people develop headaches, become drowsy, and may eventually fall into a coma. Permanent brain damage is the rule unless prompt treatment is given. Some people with tuberculous meningitis develop a tumor-like brain mass called a tuberculoma that can cause symptoms that resemble those of a stroke.
- Skin, intestines, adrenal glands, and blood vessels. All these parts of the body can be infected by M. tuberculosis. Infection of the wall of the body's main artery (the aorta) can cause it to rupture with catastrophic results. Tuberculous pericarditis occurs when the membrane surrounding the heart (the pericardium) is infected and fills up with fluid that interferes with the heart's ability to pump blood.
- Miliary tuberculosis. Miliary TB is a life-threatening condition that occurs when large numbers of tubercle bacilli spread throughout the body. Huge numbers of tiny tubercular lesions develop, causing marked weakness and weight loss, severe anemia, and gradual wasting of the body.
Diseases similar to tuberculosis
There are many forms of mycobacteria other than M. tuberculosis, the tubercle bacillus. Some cause infections that may closely resemble tuberculosis, but usually do so only when an infected person's immune system is defective. People who are HIV-positive are a good example. The most common mycobacteria that infect AIDS patients are a group known as Mycobacterium avium complex (MAC). People infected by MAC are not contagious but may develop a serious lung infection that is highly resistant to antibiotics. MAC infections typically start with an affected person coughing up mucus. The infection progresses slowly, but eventually blood is brought up and the person has trouble breathing. Among people with AIDS, MAC disease can spread throughout the body, with anemia, diarrhea, and stomach pain as common features. Often, these people die unless their immune systems can be strengthened. Other mycobacteria grow in swimming pools and may cause skin infections. Some of them infect wounds and artificial body parts such as a breast implant or mechanical heart valve. The organism that causes leprosy, M. leprae, is also related to TB.
The diagnosis of TB is made on the basis of laboratory test results. The standard test for tuberculosis, the socalled tuberculin skin test, detects the presence of infection, not of active TB. Tuberculin is an extract prepared from cultures of M. tuberculosis. It contains substances belonging to the bacillus (antigens) to which an infected person has been sensitized. When tuberculin is injected into the skin of an infected person, the area around the injection becomes hard, swollen, and red within one to three days. Today, skin tests utilize a substance called purified protein derivative (PPD) that has a standard chemical composition and is therefore is a good measure of the presence of tubercular infection. The PPD test is also called the Mantoux test. The Mantoux PPD skin test is not, however, 100% accurate; it can produce false positive as well as false negative results. These terms have specific meanings. People who have a skin reaction and are not infected are referred to having a false positive result. Those who do not react but are in fact infected are classified as having a false negative result. The PPD test is, however, useful as a screening device. Anyone who has suspicious findings on a chest x ray or any condition that makes TB more likely should have a PPD test. In addition, those in close contact with someone who has active TB or persons who come from a country where TB is common should be tested, as should all healthcare personnel and those living in crowded conditions or institutions.
Because the symptoms of TB encompass a wide range of severity and affect many parts of the body, diagnosis on the basis of external symptoms is not always possible. Often, the first indication of TB is an abnormal chest x ray or other test result rather than physical discomfort. On a chest x ray, evidence of the disease appears as numerous white, irregular areas against a dark background, or as enlarged lymph nodes. The upper parts of the lungs are most often affected. A PPD test is always performed to show whether an individual has been infected by the tubercle bacillus. To verify test results, a physician obtains a sample of sputum or a tissue sample (biopsy) for culture. Three to five sputum samples should be taken early in the morning. If necessary, sputum for culture can be produced by spraying salt solution into the windpipe. Culturing M. tuberculosis is useful for diagnosis because the bacillus has certain distinctive characteristics. Unlike many other types of bacteria, mycobacteria can retain certain dyes even when exposed to acid. This so-called acid-fast property is characteristic of the tubercle bacillus.
Body fluids other than sputum can be used for culture. If TB has invaded the brain or spinal cord, culturing a sample of spinal fluid will make the diagnosis. If TB of the kidneys is suspected because of pus or blood in the urine, culture of the urine may reveal tubercular infection. Infection of the ovaries in women can be detected by placing a tube having a light on its end (a laparoscope) into the area. Samples also may be taken from the liver or bone marrow to detect the tubercle bacillus.
In the past, treatment of TB was primarily supportive. People being treated for TB were kept in isolation, encouraged to rest, and fed well. If these measures failed, their affected lungs were collapsed surgically so that they could "rest" and heal. Today, surgical procedures still are used when necessary, but contemporary medicine relies on drug therapy as the mainstay of home care. Given an effective combination of drugs, individuals with TB can be treated at home as well as in a sanitorium. Treatment at home does not pose the risk of infecting other household members.
Most people with TB can recover if given appropriate medication for a sufficient length of time. Three principles govern modern drug treatment of TB:
- Lowering the number of bacilli as quickly as possible. This measure minimizes the risk of transmitting the disease. When sputum cultures become negative, this has been achieved. Conversely, if the sputum cultures remain positive after five to six months, treatment has failed.
- Preventing the development of drug resistance. For this reason, at least two different drugs and sometimes three are always given at first. If drug resistance is suspected, at least two different drugs should be tried.
- Long-term, continuous treatment to prevent relapse.
Five drugs are most commonly used today to treat tuberculosis: isoniazid (INH, Laniazid, Nydrazid); rifampin (Rifadin, Rimactane); pyrazinamide (Tebrazid); streptomycin; and ethambutol (Myambutol). The first three drugs may be given in the same capsule to minimize the number of pills in the dosage. As of 2001, many persons are given isoniazid and rifampin together for six months, with pyrazinamide added for the first two months. Hospitalization is rarely necessary because most persons are no longer infectious after about two weeks of combination treatment. Follow-up involves monitoring for the presence of side effects and having monthly sputum tests. Of the five medications, isoniazid is the most frequently used drug for both treatment and prevention of TB.
Surgical treatment of TB may be used if oral medications are ineffective. There are three surgical treatments for pulmonary TB: pneumothorax, in which air is introduced into the chest to collapse the lung; thoracoplasty, in which one or more ribs are removed; and removal of a diseased lung, in whole or in part. It is possible for individuals to survive with one healthy lung. Spinal TB may result in a severe deformity that can be surgically corrected.
The prognosis for recovery from TB is good for most patients, if the disease is diagnosed early and given prompt treatment with appropriate medications on a long-term regimen. Modern surgical methods have good outcomes in most cases in which they are needed. Miliary tuberculosis is still fatal in many cases but is rarely seen today in developed countries. Even in cases in which the bacillus proves resistant to all of the commonly used medications for TB, other seldom-used drugs may be tried because the tubercle bacilli have not yet developed resistance to them.
Health care team roles
Screening for tuberculosis may be conducted by nurses, physicians, physician assistants, or other trained health workers. The test is read or evaluated by a nurse, physician, or physician assistant. Treatment for TB must be prescribed and supervised by a physician. A surgeon may provide surgical intervention, often assisted by a physician assistant trained in surgery. Administration of TB medications is often supervised by nurses, although other non-medical personnel may observe TB drug ingestion. Epidemiologists collect data from many individual caregivers, and are key members of the health care team even though they do not directly provide clinical services. Pharmaceutical scientists are constantly searching for new drugs for use in treating TB.
General measures such as avoiding overcrowded and unsanitary conditions are important aspects of prevention. Hospital emergency rooms and similar locations that are used to treat or house TB patients can be treated with ultraviolet light, which has an antibacterial effect.
Vaccination is one major preventive measure against TB. A vaccine called BCG (Bacillus Calmette-Guérin, named after its French developers) is made from a weakened mycobacterium that infects cattle. Vaccination with BCG does not prevent infection by M. tuberculosis, but it does strengthen the immune system of first-time TB patients. As a result, serious complications are less likely to develop. BCG is used widely in developing countries but is not used in the United States. This is because it protects only 75% of recipients, and because everyone who receives the vaccine reacts positively to future TB screening tests. The problem is identifying the one person in four who has a false negative test result. The effectiveness of vaccination is still being studied. It is not clear whether the vaccine's effectiveness depends on the population in which it is used or on variations in its formulation.
Prophylactic use of isoniazid
Isoniazid can be given for the prevention as well as the treatment of TB. Isoniazid is effective when given daily over a period of six to 12 months to people in high-risk categories. The drug appears to be most beneficial to persons under the age of 25. Because isoniazid carries the risk of side effects (liver inflammation, nerve damage, changes in mood and behavior), it is important to administer the drug only to persons at special risk.
High-risk groups for whom isoniazid prevention may be justified include:
- Close contacts of persons with active TB, including health care workers.
- Newly infected patients whose skin test has turned positive in the past two years.
- Anyone who is HIV-positive with a positive PPD skin test. Isoniazid may be given even if PPD results are negative if there is a risk of exposure to active tuberculosis.
- Intravenous drug users, even if they are negative for HIV.
- Persons who have never been treated for TB, have positive PPD results, and show evidence of old disease on a chest x ray.
- People who have an illness or are taking a drug that can suppress the immune system.
- Persons with positive PPD results who have had intestinal surgery, have diabetes or chronic kidney failure, have any type of cancer, or are more than 10% below their ideal body weight.
- People from countries with high rates of TB who have positive PPD results.
- People from low-income groups with positive skin test results.
- Persons with a positive PPD reaction who belong to high-risk ethnic groups (African-Americans, Hispanics, Native Americans, Asians, and Pacific Islanders).
Alveolieveral small, sac-shaped cavities. In the lungs, alveoli (plural of alveolus) are found at the ends of airways, the sites where oxygen and carbon dioxide are exchanged in the blood.
Bacillus Calmette-Guérin (BCG) vaccine made from a damaged bacillus that is related to the tubercle bacillus, which may help prevent serious pulmonary TB and its complications.
Macrophage large, phagocytic cell that is found in the blood system and loose connective tissue.
Mantoux testnother name for the PPD test.
Miliary tuberculosishe form of TB in which the bacillus spreads through all body tissues and organs, producing many thousands of tiny tubercular lesions. Miliary TB is often fatal unless promptly treated.
Mycobacteria group of bacteria that includes Mycobacterium tuberculosis, the bacterium that causes tuberculosis, and other forms that cause related illnesses.
Peritonitisn infection in the peritoneum (abdominal cavity).
Pleural effusionluid that collects in the space normally occupied by a lung.
Pneumothoraxir inside the chest cavity, which may cause a lung to collapse. Pneumothorax is both a complication of pulmonary tuberculosis and a means of treatment designed to allow an infected lung to rest and heal.
Pulmonaryefers to the lungs.
Purified protein derivative (PPD)n extract of tubercle bacilli that is injected into the skin to find out whether a person presently has or has ever had tuberculosis.
Resistance property of some bacteria that have been exposed to a particular antibiotic and have changed sufficiently to survive in its presence.
Sputumecretions produced in an infected lung and coughed up. A sign of illness, sputum is routinely used as a specimen for culturing the tubercle bacillus in a laboratory.
Tuberculoma tumor-like mass in the brain that sometimes develops as a complication of tuberculous meningitis.
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American Lung Association. 1740 Broadway, New York, NY 10019. (212) 315-8700. <<a href="http://www.lungusa.org/diseases/lungtb.html">http://www.lungusa.org/diseases/lungtb.html>.
Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30333. (404) 639-3534 or (800) 311-3435. <<a href="http://www.cdc.gov/nchstp/tb/faqs/qa.htm">http://www.cdc.gov/nchstp/tb/faqs/qa.htm>.
Francis J. Curry National Tuberculosis Center. 3180 18th St., Suite 101, San Francisco, CA 94110-2028. (415) 502-4600. <<a href="http://www.nationaltbcenter.edu">http://www.nationaltbcenter.edu>.
National Tuberculosis Center, University of Medicine and Dentistry of New Jersey. 65 Bergen St., Newark, NJ 07107-3001. (973) 972-3270 or (800) 482-3627. <<a href="http://www.umdnj.edu/ntbcweb">http://www.umdnj.edu/ntbcweb>.
World Health Organization, Communicable Diseases. 20 Avenue Appia, 1211 Geneva 27, Switzerland. +41 (22) 791 4140. <<a href="http://www.who.int/gtb">http://www.who.int/gtb>.
Centers for Disease Control and Prevention. August 2001. <<a href="http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/rr4906a1.htm">http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/rr4906a1.htm>.
Columbia Presbyterian Medical Center. August 2001. <<a href="http://www.cpmc.columbia.edu/tbcpp">http://www.cpmc.columbia.edu/tbcpp>.
Department of Health Services: Australia. August 2001. <<a href="http://www.dhs.vic.gov.au/phb/hprot/tb/tbm/tb2.html">http://www.dhs.vic.gov.au/phb/hprot/tb/tbm/tb2.html>.
State Tuberculosis Control Offices. August 2001. <<a href="http://www.cdc.gov/nchstp/tb/tboffices.htm">http://www.cdc.gov/nchstp/tb/tboffices.htm>.
World Health Organization. August 2001. <<a href="http://www.who.int/gtb">http://www.who.int/gtb>.
L. Fleming Fallon, Jr., MD, PhD, DrPH
Tuberculosis (Encyclopedia of Public Health)
Tuberculosis (TB), an infectious disease, has been present throughout ancient and modern history. TB rates in the United States are on the decline after a resurgence from 1985 to 1992. However, TB continues to be a major killer in much of the world. The implications of this epidemic are global, as travel and migration are now part of everyday life.
Although the cause, diagnosis, and treatment and prevention of TB are known, paradoxically, the disease continues to increase as a public health challenge. Caused by a bacterium called Mycobacterium tuberculosis, TB spreads via an airborne route from an infectious person coughing, sneezing, laughing, or singing. The bacteria infect mainly other individuals who have frequent and prolonged contact with a contagious TB case.
TB's existence dates back many centuries. There are references to TB in third-century B.C.E. Chinese and second-century B.C.E. Indian texts; Plato and Hippocrates wrote about it around 400 B.C.E. TB was commonly known as consumption in Europe, a cause of death for hundreds of thousands in the late eighteenth and nineteenth centuries. This is when TB in close groups was first observed and assumed to have a genetic cause, since it was commonly seen in families.
In 1882 Robert Koch's discovery of Mycobacterium tuberculosis led to the recognition of TB as an infectious disease. This discovery also led to interventions for interrupting transmission from person-to-person.
Beginning in the late 1880s, TB patients were treated in sanitoria with various modalities, including exposure to fresh air, exercise, and nourishment. About 50 percent of patients recovered or had long-term remission. However, as is known today, their "cure" was not due to the treatments administered but perhaps to self-healing mechanisms.
In the early twentieth century, public health interventions became key in controlling the spread of TB in the cities, where TB was most prevalent. For example, Herman M. Biggs, General Medical Officer of New York City, actively catalogued lists of TB patients and enforced isolation and environmental mechanisms to control TB, including the opening of a TB hospital to quarantine patients. Between 1914 and 1923, the Metropolitan Life Insurance Company conducted the "Framingham Tuberculosis Project" using community nurses to visit the homes of its clients to do assessments, teach health practices, and collect data for research and policy-making purposes. The project was in response to a high rate of TB-related mortality among Metropolitan customers. As a result, mortality rates for TB in the Metropolitan pool declined by 68 percent.
Beginning in 1921, the Bacille Calmette Guerin (BCG) vaccine was used to prevent TB. Still used in many parts of the world but not in the United States, the vaccine is not effective, except perhaps in infants. The discovery of streptomycin in 1943 brought drug treatment for TB. Between 1943 and 1952, two more TB drugs, para-amino-salicylic acid (PAS) and isoniazid (INH), were discovered. Sanitoria began to close in the early 1970s, as TB could be now be treated on an outpatient basis, as evidenced by success in the decrease in TB rates with combined drug treatment and infection-control mechanisms.
By 1985, there were 22,201 cases of TB in the United States, the lowest number recorded since national case reporting began in 1953. However, rates then began to increase, until in 1992 cases peaked at 26,673. The human immunodeficiency virus (HIV) epidemic was a major contributor, as its victims are at higher risk for developing active disease once infected with TB bacteria. Migration from countries with high rates of TB added to the number. Also, improper or inadequate drug treatment for TB has led to drug-resistant strains. Finally, medical education stressed TB to a lesser degree in academic curricula, and funding and interest in TB-control programs had dwindled with decreased cases. Most authorities feel that the latter reason was the most important.
Response to the American TB resurgence resulted in increased funding for TB control programs. This gave greater access to TB treatment through health departments. The health departments were responsible not only for treating cases, but for surveillance, outreach, case management, and treatment for those who had been exposed to infectious TB cases. Directly observed therapy short course (DOTS), the observation of the ingestion of medication, has now become the basis for the worldwide standard of TB care. DOTS includes five elements: government commitment to sustained TB-control activities; case detection and self-reporting to health services; standardized treatment regimen of six to eight months for at least all confirmed infectious cases, with directly observed treatment (DOT) for at least the initial two months; a regular, uninterrupted supply of all essential anti-TB drugs; and a standardized recording and reporting system that allows assessment of treatment results for each patient and of the TB control program overall. DOTS is presently available to 25 percent of the world's TB patients, but its acceptance is slowly increasing. There was also an increase in TB educational interventions via the public health sector and medical schools. New drug trials did not create new drugs but created variations on existing drugs and regimens. TB rates began to decrease again in 1994, and as of 1999, they were at an all-time low of 17,528 cases in the United States. Globally, there are still eight million new cases of TB annually with three million deaths. Clearly, even with the exemplary level of achievement domestically, TB cannot be controlled anywhere unless it is controlled everywhere.
Although one of the Healthy People 2010 goals calls for TB elimination from this country, the United States is still far from that goal. Many interventions need to be continued despite falling rates. For other communicable diseases, effective vaccine development and the advent of new drug therapies has been key to disease control approaching elimination. The best course for TB elimination is to develop a vaccine and new drugs while continuing surveillance, treating TB patients who may infect others, treating those who have been infected but are not yet active cases, increasing TB awareness among health professionals, and performing targeted testing for TB infection among high-risk populations. This combination of medical and public health practice can make TB elimination a reality.
RAJITA R. BHAVARAJU
LEE B. REICHMAN
(SEE ALSO: Communicable Disease Control; Drug Resistance; Immunizations; Isolation)
Centers for Disease Control and Prevention (1995). Self-Study Modules on Tuberculosis. Atlanta, GA: Author.
(2000). Core Curriculum on Tuberculosis: What the Clinician Should Know, 4th edition. Atlanta, GA: Author.
Daniel, T. M. (1997). Captain of Death: The Story of Tuberculosis. Rochester, NY: University of Rochester Press.
Dublin, L. I. (1952). A Forty-Year Campaign against Tuberculosis: The Contribution of the Metropolitan Life Insurance Company. New York: Metropolitan Life Insurance Company.
Reichman, L. B. and Tanne J. H. (2001). Time Bomb: The Global Epidemic of Multidrug Resistant Tuberculosis. New York: McGraw Hill.
Tuberculosis (World of Microbiology and Immunology)
Tuberculosis (TB) is an infectious disease of the lungs caused by the bacterium Mycobacterium tuberculosis. In the mid-nineteenth century, about one-fourth of the mortality rate was attributable to tuberculosis. It was particularly rampant in early childhood and young adulthood. Its presence was felt throughout the world, but by the 1940s, with the introduction of antibiotics, there was a sharp decline of cases in developed countries. For less-developed countries with poor public health structures, tuberculosis is still a major problem. Since 1989, however, there has been an increase in reported cases in economically advanced countries due mainly to immunosuppression associated with AIDS, and the emergence of antibiotic-resistant strains of TB.
The bacillus infects the lungs of those who inhale the infected droplets formed during coughing by an individual who has an active case of the disease. It can also be transmitted by unpasteurized milk, as animals can be infected with the bacteria. The disease is dormant in different parts of the body until it becomes active and attacks the lungs, leading to a chronic infection. Symptoms include fatigue, loss of weight, night fevers and chills, and persistent coughing with sputumstreaked blood. The virulent form of the infection can then spread to other parts of the body. Without treatment, the condition is eventually fatal.
Chest x rays and sputum examinations can show the presence of tuberculosis. Tuberculin, a purified protein taken from the tuberculosis bacilli, is placed under the skin of the forearm during a tuberculosis skin test. In two or three days if there is a red swelling at the site, the test is positive, and indicates TB infection, but not necessarily active TB disease. Early detection of the disease facilitates effective treatment to avoid the possibility of it becoming active later on.
Populations at risk of contracting TB are people with certain medical conditions or those using drugs for medical conditions that weaken the immune system. Others at risk are low-income groups, people from undeveloped countries with high TB rates, people who work in or are residents of long-term care facilities (nursing homes, prisons, hospitals), those who are significantly underweight, alcoholics, and intravenous drug users.
Traces of lesions from tuberculosis have been found in the lungs of ancient Egyptian mummies. The recent discovery of a Pre-Columbian mummy has resolved the debate on whether or not European explorers introduced the disease to the New World. Lung samples from a Peruvian woman who lived 500 years before Columbus discovered America show a lump that was identified as tuberculosis by DNA testing. Hippocrates, a Greek physician who lived from 460 to 370 B.C., described the disease. The Greek name for the disease was phthisis, derived from the verb phthinein, meaning to waste away. Tuberculosis was also called consumption because of the wasting away effects (notably, significant losses of weight over a period of time) of the disease.
In 1839, Johann Schonlein is credited with first labeling the disease tuberculosis. In 1882, the tubercle bacillus was discovered by Robert Koch, the German physician who pioneered the science of bacteriology. This landmark discovery was followed eight years later by his extraction of a protein from dead bacilli called tuberculin. This protein is still used to test for the presence of TB infection in a dormant or early stage. Another important diagnostic breakthrough came in 1895 with the discovery of Wilhelm Conrad Roentgen's x rays. The presence of TB lesions was detected on x rays.
Two twentieth century French scientists, Albert Calmette and Camille Guerin, developed a vaccine against tuberculosis from a weakened strain of bovine bacillus. Called BCG for Bacillus-Calmette-Guerin, this vaccine is the only
The CDC still recommends the use of skin tests and drug therapy as the most important measures in controlling the incidence of TB in the United States. Drug therapy is 90% effective in halting the infection. Since those vaccinated test positive with the skin test, a vaccination program would interfere with skin testing. Mass vaccination would risk giving up a simple test that provides an early warning. Relying on the drug treatment program to stop TB epidemics, however, has one major drawback. The drug therapy takes six months to a year before halting the infection. People infected are often among the homeless, poor, drug addicted, or criminal societies. Unless these people are carefully supervised to make sure they complete a regimen of drug therapy, it is difficult to effect a cure for the disease.
Throughout the nineteenth century and up until the 1960s, physicians sent their TB patients to sanatoriums which were rest homes located in mountains or semi-arid regions such as the American southwest. These locations were supposed to help the breathing process by providing clean and dry air. Physicians assumed that deeper, easier breathing in a work-free environment would help overcome the disease. Prior to the advent of antibiotics, these retreats were the only recourse for chronically ill tubercular patients. Although treatment in sanatoriums did help many, they were phased out before the 1960s, and replaced by antibiotic drug chemotherapy, which could be administered in either a hospital or home environment. Over 90% of TB patients can be cured by a combination of inexpensive antibiotics, but it is necessary they be used for a period of at least six months.
The impact of tuberculosis was evident in the nineteenth and early twentieth centuries in literature, art, and music. Puccini's opera, La Boheme, was created around the tragic death of the tubercular heroine, Mimi. Since TB often attacked the young, many poets, artists and musicians fell prey to the disease before they had a chance to fulfill their creative work. Among them, Amedeo Modigliani, John Keats, Frederic Chopin, and Anton Chekhov were claimed by the disease, along with millions of other young people during the period. In the United States, American playwright Eugene O'Neill was one of the fortunate few who did recover in a sanatorium and went on to write his plays. His early play, The Straw, written in 1919, dramatically shows what life was like in a sanatorium.
In the past, U.S. city and state governments were actively involved in regulations that controlled infected people from spreading the infection. At present, federal, state, and local agencies must again take a leading role in formulating a public policy on this complicated health problem. Several states are using a program called Directly Observed Therapy (DOT) to combat the rising incidence of TB. This program has met with considerable success in lowering reported cases of TB as much as 15% in New York City during the late 1990s.
DOT is offered at soup kitchens, clinics, hospitals, neighborhood health centers, and drug rehabilitation centers. Outreach workers enable those with TB to get help with the least amount of red tape. The wide array of medicines needed to treat the disease are made available, and ample funding has been provided from federal, state, and local agencies. Apartments are located for homeless patients and special provisions are made to help released prison inmates and those on parole. Guidelines for compassionate, supervised medical services are periodically reviewed for the successful implementation of the DOT program.
Despite such measures, the U.S. Department of Health and Human Services predicts tuberculosis, will spread further by the year 2005. In 1990, there were 7,537,000 TB cases worldwide. That number is expected to rise to 11,875,000 in 2005, a 58% increase. Most of the rise in rate is attributed to demographic factors (77%) while 23% accounts for the epidemiological factors, i.e., the rise in HIV infection. Approximately 30 million people around the world will die of TB from 2000 to 2009. These predictions are considered conservative because many cases of TB are never reported.
See also AIDS, recent advances in research and treatment; Bacteria and bacterial infection; Epidemiology, tracking diseases with technology; Public health, current issues