Investigation to determine the source case could be conducted in at least two circumstances: 1) when a health-care setting detects an unexplained cluster of TST conversions among HCWs or 2) when TB infection or disease is diagnosed in a young child. The purposes of a source case investigation are to ascertain that the source case has been diagnosed and treated, to prevent further M. tuberculosis transmission, and to ensure that other contacts of that source case are also evaluated and, if indicated, provided treatment.

OTHER DEFINITIONS