Tuberculosis (commonly abbreviated as TB) is an infectious disease caused by an agent called Mycobacterium tuberculosis (M. tuberculosis). Tuberculosis can be potentially life-threatening; if treated properly with drugs, however, chances of recovery are very high. Tuberculosis used to be the number one cause of death in the United States and Europe until the first part of the 20th century.
Since the discovery of drugs specific to tuberculosis (tuberculosis chemotherapy) in the 1940s and 50s, the number of people with disease in this country started to decrease significantly. This trend began to reverse in the mid-1980s and many specialists believe that tuberculosis still presents a public health threat.
Tuberculosis is caused by several species of Mycobacterium, which are collectively called tubercle bacillus. In most cases in humans (nearly 90 percent), tuberculosis primarily affects the lungs (pulmonary TB). But it can also affect other organs in the body, such as the intestines, genital organs, kidneys, bladder, and even skin, bones and joints (extrapulmonary TB). A person can get infected with tuberculosis by inhaling the air breathed or coughed out by an infected patient, or, as is the case much more rarely, by drinking milk from infected animals.
A differentiation is commonly made between tuberculosis infection and active TB disease. The key difference here is that a person with a tuberculosis infection will test positive for TB, but will not exhibit any symptoms. Once the person becomes symptomatic and is contagious, he or she is said to have active tuberculosis.
Several risk factors for tuberculosis have been identified:
- contact with an infected person or person exhibiting symptoms of active TB (in rare cases, contact with an infected animal may also lead to infection)
- young age (infants and children have weaker immune systems than adults)
- weakened immune system due to aging or a different disease that affects the immune system, such as HIV/AIDS
Because it is easier for a person with a weaker immune system to get infected with tuberculosis, it primarily affects young children and the elderly. Once infected, however, the person can then develop active disease (begin having symptoms) at any age.
Other risk factors that contribute to the ease with which tuberculosis is spread include overcrowding, lack of sanitary living conditions, and poor hygiene. That is why tuberculosis now is a much bigger problem in developing countries than in the United States. But there are similar problems in this country in places like prisons and some shelters; that’s why prisons are often called the “breeding grounds” for such diseases as TB and AIDS. Also, the fact that there are still a lot of people immigrating to the United States from all over the world, including the countries where TB is a big problem, is another reason for the plateau of tuberculosis rates in this country. TB disproportionately affects the immigrant population in the United States.