Recurrence of tuberculosis in a low incidence setting

¹ Respiratory Dept, Liverpool Hospital, Sydney, New South Wales, Australia
² Centre for Infectious Diseases and Microbiology, Institute of Clinical Pathology and Medical Research, Westmead Hospital, Sydney, New South Wales, Australia

^* To whom correspondence should be addressed. E-mail: ccdobler{at}yahoo.com.

	Abstract

Recurrence of active tuberculosis after treatment of an initial disease episode can be due to endogenous reactivation or exogenous reinfection.

Cases of recurrent tuberculosis in the Australian state of New South Wales between 1994 and 2006 were identified by data linkage analysis with confirmatory review of case notes. We included patients with more than one culture positive disease episode during that time period who had completed treatment for the initial disease episode. Genotyping of Mycobacterium tuberculosis was used to determine whether recurrence was likely to be due to reactivation or reinfection.

There were 5723 tuberculosis notifications between 1994 and 2006, of which 3731 were culture positive. Fifteen patients (0.4%) had recurrent culture positive disease over an average 5.7 years of follow-up (crude annual incidence, 71/100,000). Recurrent tuberculosis was attributable to reactivation (indistinguishable strains) in 11 (73%) cases and to reinfection (different strains) in 4 cases (27%).

In a low incidence setting for tuberculosis, a control program incorporating directly observed therapy for active disease results in a very low rate of recurrent tuberculosis over a long period of follow-up. Reinfection is less likely than reactivation, but still contributes significantly to the number of cases with recurrent disease.