Exogenous re-infection as a cause of recurrent tuberculosis in a low-incidence area.

SETTING: Surveillance data from the National Tuberculosis Register for the period 1993-1997 complemented with DNA fingerprinting results of Mycobacterium tuberculosis isolates. OBJECTIVE: To estimate the proportion of disease attributable to recent re-infection among Dutch tuberculosis patients with reported tuberculosis infection or disease before 1981. DESIGN: Data from 1,547 Dutch patients diagnosed between 1994 and 1997 in the Netherlands were studied. Cases with reported tuberculosis infection or disease before 1981 were attributed to reactivation if their M. tuberculosis isolate was unclustered based on DNA fingerprinting or if they were the first case in a cluster, and to re-infection if they were clustered, but not as the first case. RESULTS: In total, 183 Dutch tuberculosis patients (12%) had reported tuberculosis infection or disease before 1981. Tuberculosis in 29 of these patients (16%) was attributed to recent re-infection. CONCLUSION: In this setting with a low tuberculosis incidence, approximately one in six new disease episodes among patients with previous tuberculosis infection or disease may be attributable to recent re-infection.