Outbreak of tuberculosis associated with a floating card game in the rural south: lessons for tuberculosis contact investigations.

We investigated an outbreak of tuberculosis disease and infection in a rural southern county in which an average of less than one case per year had occurred in the previous 10 years. Nine cases of tuberculosis developed. Reinterview 19 months after the patient with the initial case presented revealed that he had participated in an illegal floating card game with two of the other patients; numerous other unacknowledged social connections among the patients existed. Restriction fragment length polymorphism typing revealed that mycobacteria isolated from five of six available specimens matched; the patient from whom the nonmatched mycobacterium was isolated had a coincident relapsed case. The infection rate among contacts decreased as the investigation expanded to include more than one-third of the county residents: from 51% of those named initially to 2% of those at a school screening and from 68% of those named by more than one patient to 20% of those named by only one patient. Maintaining effective tuberculosis control programs in areas in which the incidence is low will be a challenge as rates of tuberculosis continue to decline nationwide.