The role of molecular epidemiology in contact investigations: a US perspective.

Preventing tuberculosis (TB) transmission through treatment of active cases and contact investigation is the highest priority of TB control programs in the United States. The role of contact investigation is becoming increasingly important as the number of TB cases declines nationally. However, the effectiveness of contact investigation has been difficult to assess because, prior to the availability of molecular genotyping techniques, levels of transmission were crudely measurable. Epidemiological links within and outside the traditional concentric circle approach are limited by the quality of the contact investigation, the skill and knowledge of the investigator and the information provided by the patient. Molecular epidemiology has added a new dimension by enabling the recognition of unsuspected transmission, likely locations of transmission, and quantification of the extent of transmission that is occurring within a given population. In the future, as real-time genotyping becomes more available, the role of molecular epidemiology is likely to expand.