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1. What is tuberculosis?
2. How does a person get TB?
3. What happens to the body when a person gets TB?
4. How does it affect the body?
5. What are the symptoms?
6. Who's affected?
7. How's it treated?
8. TB Links
1. What is tuberculosis?
tu·ber·cu·lo·sis (tʊ-bûr'kyə-lō'sĭs, tyʊ-)
An infectious disease of humans and animals caused by the tubercle bacillus and characterized by the formation of tubercles on the lungs and other tissues of the body, often developing long after the initial infection. Tuberculosis of the lungs, characterized by the coughing up of mucus and sputum, fever, weight loss, and chest pain.
2. How does a person get TB?
A person can become infected with tuberculosis bacteria when he or sheinhales minute particles of infected sputum from the air. The bacteria get into the air when someone who has a tuberculosis lung infection coughs, sneezes, shouts, or spits (which is common insome cultures). People who are nearby can then possibly breathe the bacteria into theirlungs. You don't get TB by just touching the clothes or shaking the handsof someone who is infected. Tuberculosis is spread (transmitted) primarily from personto person during close contact by breathing infected air.
There is a form of tuberculosis, however, that is transmitted by drinking unpasteurized milk. Related bacteria, called Mycobacterium bovis, cause this form of TB. It previously was a major cause of TB in children, but rarely causes TB now since most milk is pasteurized (a heating process that kills thebacteria).
3. What happens to the body when a person gets TB?
When the inhaled tuberculosis bacteria enter the lungs, they can multiply,causing a local lung infection (pneumonia). The local lymph nodes associated with the lungs may also become involved. In addition, TB can spread to other parts of the body. The body's immune (defense) system, however, can fight off the infection and stop the bacteria from spreading. The immune system does so ultimately by forming scar tissue around the TB bacteria and isolating it fromthe rest of the body.
If the body is able to form scar tissue (fibrosis) around the TB bacteria, then the infection is contained in an inactive state. Such an individual typically has no symptoms and cannot spread TB to other people. The scar tissue and lymph nodes may eventually harden, like stone. (That is, these scars and nodescan calcify.)
4. How does it affect the body?
TB most commonly affects the lungs but can affect almost any part of the body. It can be spread when someone with the infection coughs or sneezes or talks and another person breathes in the bacteria. However, prolonged contact is usually needed to become infected.
5. What are the symptoms?
Initially there may be no symptoms. When symptoms develop they commonly include:
- a persistent cough - usually for more than three weeks - initially it may be dry and then is accompanied by sputum that may be blood-streaked
- night sweats for weeks or months
- weight loss
- fatigue
- high temperature
- shortness of breath
6. Who's affected?
It's estimated that a third of the world's population is infected with the bacteria that causes TB. Each year about 8 million people develop the disease and up to 2.5 million people worldwide are killed by it. In the UK there are about 8,000 cases a year.High-risk populations
Anyone can get TB. People at greater risk of developing TB include:- children and older people
- smokers
- those living in overcrowded conditions
- those who have a poor diet
- people with HIV
- the homeless
The elderly
Tuberculosis is more common in elderly persons. More than one-fourth of the nearly 23,000 cases of TB reported in the United States in 1995 developed in people above age 65. Many elderly patients 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 ward off the tubercle bacillus. Finally, bacteria that have lain dormant for some time in elderly persons may be reactivated and cause illness.
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 remedied, there is no real possibility of completely eliminating the disease.
7. How's it treated?
Supportive care
In the past, treatment of TB was primarily supportive. Patients were kept in isolation, encouraged to rest, and fed well. If these measures failed the lung was collapsed surgically so that it 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, patients 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.
Drug therapy
Most patients 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 remains 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 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 1998, many patients are given INH and rifampin together for six months, with pyrazinamide added for the first two months. Hospitalization is rarely necessary because many patients are no longer infectious after about two weeks of combination treatment. Follow-up involves monitoring of side effects and monthly sputum tests. Of the five medications, INH is the most frequently used drug for both treatment and prevention.
Surgery
Surgical treatment of TB may be used if 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 patients to survive with one healthy lung. Spinal TB may result in a severe deformity that can be corrected surgically.
Prognosis
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 a good outcome 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.
Prevention
General measures
General measures such as avoidance of overcrowded and unsanitary conditions are also necessary aspects of prevention. Hospital emergency rooms and similar locations can be treated with ultraviolet light, which has an antibacterial effect.
Vaccination
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 more widely in developing countries than in the United States. 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.
Sources: BBC Health, Medicine.net
8. TB links
Global Alliance for TB Drug Development
Global TB Drug facility
International Union Against TB and Lung Disease
Management of tuberculosis: a guide for low-income countries
Recent WHO publications on TB and HIV |
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