Mycobacterium tuberculosis

          Mycobacterium tuberculosis is the organism responsible for the disease tuberculosis in humans.  Although tuberculosis is traditionally considered an “old” disease because of its occurrence throughout history, TB poses a major health concern even in the twenty-first century.  Worldwide about 8 million new cases of tuberculosis are reported every year, of which over 22,000 are reported in the United States (Figure 1).  In addition, between 10 and 15 million people in the U.S. already have the bacteria lying dormant in their lungs, so they have the potential to develop active tuberculosis disease at any time.  (See the “Pathogenesis” section to learn the difference between latent tuberculosis infection and active tuberculosis disease.”)

          One of the main contributors to the rise in TB disease since the 1980’s is the increased incidence of persons infected with HIV.  Since HIV severely compromises the immune systems of those with the condition, the virus heightens the chance of progressing from latent tuberculosis infection (LTBI) to active tuberculosis disease.  Growing rates of poverty, homelessness, and drug abuse are also to blame for the increase in TB disease during the latter part of the twentieth century.
 

          Just as certain immunocompromising conditions and lifestyle choices put a person at high-risk for developing TB disease from LTBI, some individuals have a greater likelihood of being exposed to and infected with M. tuberculosis.  These people include the following:
•  Poor or homeless persons
•  Healthcare workers who serve patients with tuberculosis
•  Residents and employees of communal living settings such as prisons, nursing homes, shelters, etc.
•  Foreign-born persons who have arrived to the U.S. from countries with a high prevalence of TB
•  Family members, friends, and coworkers who are in close contact with someone who has TB disease

This website was created by Ashley Millard.

Last updated April 25, 2007.