20.7 TB Example

The causative agent is Mycobacterium tuberculosis. It has a 5-year mortality of 65%. Approximately 5 million cases were reported in 2005 (6). TB occurs in developing countries but has become increasingly more common in the United States. It is increasingly more dangerous, as there are several drug-resistant variants that have made effective definitive treatment much more difficult. Transmission is via respiratory droplets from those with active tuberculosis. The development of active disease really depends more on the host's immune response. Approximately 10% of those infected with latent TB will develop active disease. There are several types of extrapulmonary forms of tuberculosis that may result from a long-term tuberculosis infection.