y: In the U.S. today, tuberculosis is solely transmitted by inhaling indoor air contaminated with Mycobacterium tuberculosis (1:887). The air is contaminated by a person with active tuberculosis coughing out bacteria into the it. A fetus may acquire tuberculosis from its mother during birth by breathing in or swallowing infected amniotic fluid. In developing countries, children may become infected with other mycobacterium which cause tuberculosis. Mycobacterium bovis may be transmitted in unpasteurized milk (1:887).
The immune system of a person infected with tuberculosis usually destroys the bacteria or seals them off at the site of infection. Sometimes the bacteria aren't destroyed and lay dormant inside white blood cells for many years. About 80 percent of tuberculosis infections are caused by activation of dormant bacteria, which can occur when a person's immune system becomes impaired, for instance in AIDS. Wilkinson and Gilks (1998) found that the HIV epidemic is having a substantial impact on the health of hospital staff treating such patients, tuberculosis being more common among these workers. Granich et al (1998) studied an immigrant population in three Florida counties and found that 49
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