Tuberculosis (TB)

tuberculosis

tuberculosis (TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the intestines, bones and joints, the skin, and the genitourinary, lymphatic, and nervous systems may also be affected.

There are three major types of tubercle bacilli that affect humans. The human type (Mycobacterium tuberculosis), first identified in 1882 by Robert Koch, is spread by people themselves. It is the most common one. The bovine type (M. bovis) is spread by infected cattle but is no longer a threat in areas where pasteurization of milk and the health of cattle are strictly supervised. The avian type (M. avis) is carried by infected birds but can occur in humans. The tubercle bacillus can live for a considerable period of time in air or dust. The most common means of acquiring the disease is by inhalation of respiratory droplets.

Course of the Disease

Tuberculosis of the lungs usually results in no or minimal symptoms in its early stages. In most persons the primary infection is contained by the body's immune system, and the lesion, called a tubercle, becomes calcified. In many the infection is permanently arrested. In others the disease may break out again and become active years later, usually when the body's immune defenses are low. Untreated, the infection can progress until large areas of the lung and other organs are destroyed. Symptoms of the disease include cough, sputum, bleeding from the lungs, fever, night sweats, loss of weight, and weakness.

Incidence

The incidence of tuberculosis of the lungs, the "white plague" that formerly affected millions of people, declined in the United States from the 1950s until 1984; sanatoriums were closed and routine screening was abandoned. Then, between 1984 and 1992, the incidence increased by 20%, chiefly because of immigration from countries where it is common and because of AIDS, which leaves people particularly vulnerable to the disease. Renewed efforts at control and advances in treatment have been rewarded with incidence declines each year, amounting to a total decline of 31% from 1992 to 1998.

Worldwide the outlook has been far less encouraging. In 1993 the World Health Organization (WHO) declared TB a global health emergency. Approximately one third of the world's population is infected; an estimated 1.3 million died in 2012. The vast majority of new cases occur in sub-Saharan Africa. Spread of TB is especially rapid in areas with poor public health services and crowded living conditions. In homeless shelters and prisons, crowded conditions and inadequate treatment often go together. Areas where living conditions are disrupted by wars, famine, and natural disasters also are heavily affected.

Especially alarming has been the spread of drug-resistant strains of TB. By the late 1990s scientific experts and international health officials warned that drug-resistant strains were spreading faster than had been anticipated. Bacteria can survive and become drug resistant in patients whose treatment is not properly monitored and seen to completion. Multidrug resistant (MDR) TB strains are resistant to two or more of the commonly prescribed first-line drugs, while extensively drug resistant (XDR) strains are also resistant to three or classes of the more toxic second-line drugs. Some believe that unless major new treatment strategies are initiated in source countries, drug-resistant TB will eventually become epidemic even in areas with good control programs, such as Europe and America. In 2011, WHO estimated that there were more than 80,000 cases, many of them undiagnosed, of drug-resistant TB in Europe.

Diagnosis and Treatment

Diagnosis is made by a tuberculin skin test. It can be confirmed by X rays of the chest and sputum examination. Ideally, treatment begins after a skin test signals exposure but before active disease has developed. The treatment of choice for prevention and for active cases is the antimicrobial drug isoniazid (INH), available since 1956. In infected individuals it now is usually used in combination with other antituberculosis drugs such as rifampin, pyrazinamide, and ethambutol. Bedaquiline is used to treat multidrug resistant and extensively drug resistant TB.

Tuberculosis drugs have to be taken regularly, typically for 6 to 12 months. Many patients abandon their treatment when they feel better; similarly, preventive treatment is often abandoned because of the inconvenience. Such noncompliance is believed to be the main reason for the upsurge in drug-resistant strains of the TB bacilli, many of which are resistant to more than one drug. Drug-resistant TB is difficult to treat and has a much higher death rate; extensively resistant TB is especially worrisome because it can be essentially untreatable.

The combination drug rifater (rifampin, isoniazid, and pyrazinamide) has simplified drug administration. Directly observed treatment, where health-care workers watch patients take each dose of medicine, has proved effective in eliminating the problem of noncompliance in the United States, but monitoring has been less effective in many other parts of the world.

Prevention of Tuberculosis

Preventive measures include strict standards for ventilation, air filtration, and isolation methods in hospitals, medical and dental offices, nursing homes, and prisons. If someone is believed to have been in contact with another person who has TB, preventive antibiotic treatment may have to be given. Infected persons need to be identified as soon as possible so that they can be isolated from others and treated.

An antituberculosis vaccine, bacille Calmette-Guérin, or BCG vaccine, was developed in France in 1908. Although there is conflicting evidence as to its efficacy (it appears to be effective in 50% of those vaccinated), it is given to over 80% of the world's children, mostly in countries where TB is common; it is not generally given in the United States. Federal health officials in the United States have stated (1999) that a new vaccine is essential to TB prevention. It is hoped that the determination of the complete DNA (genome) sequence of Mycobacterium tuberculosis, achieved in 1998, will hasten the development of an effective vaccine.

Bibliography

See R. Dubos, The White Plague (1955); S. A. Waksman, The Conquest of Tuberculosis (1964).

The Columbia Encyclopedia, 6th ed. Copyright© 2015, The Columbia University Press.

Tuberculosis (TB): Selected full-text books and articles

Tuberculosis By Carol A. Dyer Greenwood, 2010
Infectious Fear: Politics, Disease, and the Health Effects of Segregation By Samuel Kelton Roberts Jr University of North Carolina Press, 2009
Collaboration Is Key for New Global Tuberculosis Strategy By Fleck, Fiona Bulletin of the World Health Organization, Vol. 92, No. 5, May 2014
PEER-REVIEWED PERIODICAL
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
Tuberculosis: A Global Health Problem By Zaman, K Journal of Health Population and Nutrition, Vol. 28, No. 2, April 2010
PEER-REVIEWED PERIODICAL
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
Lives Saved by Tuberculosis Control and Prospects for Achieving the 2015 Global Target for Reducing Tuberculosis Mortality By Glaziou, Philippe; Floyd, Katherine; Korenromp, Eline L.; Sismanidis, Charalambos; Bierrenbach, Ana L.; Williams, Brian G.; Atun, Rifat; Raviglione, Mario Bulletin of the World Health Organization, Vol. 89, No. 8, August 2011
PEER-REVIEWED PERIODICAL
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
Disease and Mortality in Sub-Saharan Africa By Dean T. Jamison; Richard G. Feachem; Malegapuru W. Makgoba; Eduard R. Bos; Florence K. Baingana; Karen J. Hofman; Khama O. Rogo World Bank, 2006
Librarian’s tip: Chap. 13 "Tuberculosis"
Pathologies of Power: Health, Human Rights, and the New War on the Poor By Paul Farmer University of California Press, 2003
Librarian’s tip: Chap. 7 "Cruel and Unusual Drug-Resistant Tuberculosis as Punishment" and Chap. 4 "A Plague on All Our Houses? Resurgent Tuberculosis inside Russia's Prisons"
Health Policy in a Globalising World By Kelley Lee; Kent Buse; Suzanne Fustukian Cambridge University Press, 2002
Librarian’s tip: Chap. 10 "The Globalisation of Dots: Tuberculosis as a Global Emergency"
The Epidemic Streets: Infectious Disease and the Rise of Preventive Medicine, 1856-1900 By Anne Hardy Clarendon Press, 1993
Librarian’s tip: Chap. 8 "Tuberculosis"
The Divided Path: The German Influence on Social Reform in France after 1870 By Allan Mitchell University of North Carolina Press, 1991
Librarian’s tip: Chap. 11 "The Parable of Tuberculosis"
Tuberculosis Control in Alberta: A Federal, Provincial and Regional Public Health Partnership By Long, Richard Canadian Journal of Public Health, Vol. 93, No. 4, July/August 2002
"Hardly a Family Is Free from the Disease": Tuberculosis, Health Care, and Assimilation Policy on the Nez Perce Reservation, 1908-1942 By James, Elizabeth Oregon Historical Quarterly, Vol. 112, No. 2, Summer 2011
PEER-REVIEWED PERIODICAL
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
A Nurse Contracts Tuberculosis on the Job, 1944-45 By Golden, Janet Nursing History Review, Vol. 16, January 1, 2008
PEER-REVIEWED PERIODICAL
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
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