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History and Treatment of Tuberculosis

May 1st, 2007

This essay describes the definition, symptoms, methods of treatment, and a brief historical chronology of the disease tuberculosis, often abbreviated TB.

Definition and Characteristics:

Tuberculosis (abbreviated TB) is a highly infectious, sometimes fatal disease that is caused by the bacteria Mycobacterium tuberculosis. It is characterized by the formation of hard nodules (tubercles) on lung or bone tissue. Although it is possible for any organ of the body to be affected by TB, infection of the lungs is by far the most common. The disease is contracted by inhalation of respiratory droplets that have been discharged into the air by an infected person or animal. However, it is not possible to contract TB by physical contact such as handshakes, use of toilet seats, or the use of shared dishes or utensils.

Symptoms:

Most people who become infected with TB do not exhibit any initial symptoms of the disease. However, the bacteria can lie dormant in the body for several years, and may become active if the person’s immune system is weakened. Symptoms of active TB disease are cough, sputum, bleeding from the lungs, night sweats, loss of appetite, weight loss, and a low-grade fever. If left untreated, the infection can eventually destroy large areas of the lungs or spread to other areas of the body such as the kidneys, brain, or spine. Miliary tuberculosis is an especially dangerous form of TB in which large numbers of bacteria enter the bloodstream, causing many tiny tubercular lesions to form, leading to severe anemia and a gradual wasting of the body. It is almost always fatal unless it is promptly treated.

Diagnosis:

An initial diagnosis of TB can be made by administering a tuberculin skin test. If the test is positive, doctors will usually perform a chest X-ray and an examination of sputum (phlegm that is coughed up from the lungs). These will definitively confirm the presence or absence of TB. If a skin test is negative, a second skin test may be administered several weeks later. If this is also negative, the possibility of TB can be effectively ruled out in the vast majority of cases.

Treatment and Prevention:

When a person is diagnosed with TB, the most effective treatment consists of a four-drug regimen of isoniazid (INH), rifampin, pyrazinamide, and ethambutol. These medicines must be taken regularly (usually about 2-3 times per week) for 6 to 12 months, depending on the severity of the infection, for the treatment to be completely effective. It is very important that these medications are taken consistently for the full length of the prescribed time period. When patients are very inconsistent in taking these medications, or if they stop taking them once they begin to feel better and do not complete the full treatment cycle, drug-resistant strains of TB may develop. These resistant strains are much more difficult to treat, and the side effects of the additional drugs required for such treatment are usually much greater than those for the standard treatment. The fatality rate for drug-resistant TB strains is also much higher.

The standard antibiotic treatment for TB can also be used as a preventive measure for people who test positive for latent TB but have not yet developed the active disease. Thus it is important for people who believe that they may have been exposed to TB or who are at a high risk for contracting TB to receive testing. Other preventive measures include the use of strict standards for ventilation, air filtration, and isolation methods in hospitals, dental offices, nursing homes, prisons, or other buildings where TB patients may be present. There is a vaccine for TB called Bacilli Calmette-Guerin, or BCG, but it is only effective in about 50% of people who are vaccinated. This vaccine is very seldom used in the United States because of its perceived unreliability, but it is frequently administered to children in other parts of the world where TB is more common. In the United States, it is hoped that the discovery of the complete DNA of Mycobacterium tuberculosis in 1998 will lead to the development of a much more effective vaccine in the near future.

History:

Tuberculosis has been one of the most common and persistent diseases throughout human history. Evidence of TB has been found in mummies and skeletons dating from as early as 2400 BC. The ancient Greeks called TB phthisis, or “consumption”, a term that was commonly used until the middle of the 20th century. In medieval times, TB was known as the “white plague” and was widely feared. It was sometimes confused with leprosy, and for this reason, people who were infected with TB were often shunned and isolated by most medieval societies. By the 17th and 18th centuries, many physicians and scientists began to seriously study TB, and some of them began to conjecture that the disease might be caused by some type of “minute living creature”.

In the 1850’s, the development of the sanatorium represented the first major step in controlling the spread of TB. This allowed TB patients to receive good supportive care under proper sanitary conditions. Finally, in 1882, Robert Koch managed to develop a staining technique that enabled people to actually see the Mycobacterium tuberculosis specimen. This put to rest the persistent myth that “consumption” could arise spontaneously within an individual person.

Once the actual bacteria had been identified, the real search for an effective cure could begin. The first success came in 1943 when doctors developed an antibiotic called streptomycin. Other important antibiotics such as isoniazid, ethambutol, and rifampin were developed in the 1950’s and 1960’s, and during this period, the incidence of TB declined rapidly, leading many people to believe that TB had been effectively eradicated. However, in the mid-1980’s, approximately coinciding with the discovery of the AIDS virus, TB began to resurface. In the 1990’s, renewed efforts aimed at preventing the spread of both TB and AIDS brought the disease under control again for the most part, although TB is still a significant problem in many underdeveloped countries. Today, most of the research in the area of TB treatment is focused on developing methods of battling persistent drug-resistant strains of TB.


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