Rethinking Tuberculosis Epidemiology: the Utility of Molecular Methods Working within a classic TB control framework while using newer molecular techniques, epidemiologists are reevaluating M. tuberculosis

lthough effective chemotherapy for treating disease caused by Mycobac- terium tuberculosis infections has been available since the early 1950s, the morbidity and mortality attrib- uted to this pathogen remain alarmingly high, especially in poor countries and in those lacking a good tuberculosis (TB) control infrastructure. Other factors, including the ongoing HIV/AIDS pandemic, complicate efforts to control TB. Outcome differences among in- dividuals who are infected with M. tuberculosis were pivotal in for- mulating basic hypotheses regard- ing the pathogenesis and transmis- sion of this bacillus. For example, approximately one-third of those exposed to these bacilli show evi- dence of infection during the course of their lives, but, of those infected, only 10% ever become ill or pass the pathogen on to others. Individuals also vary in terms of disease severity, duration, and type of symptoms that they develop. It is com- monly believed that these differences are due to host-environmental factors and host-pathogen interactions.