Rationale: In 2002, a mobile radiographic screening program was started in Rotterdam to respond to high rates of tuberculosis (TB) among illicit drug users and homeless persons.
Objectives: We studied trends and characteristics of TB among these risk groups and assessed the impact of the screening program on transmission, using molecular typing.
Methods: Description of trends, and of demographic and disease-related characteristics of tuberculosis cases among these risk groups between 1993 and 2005. TB was considered to result from recent transmission if the mycobacterial DNA fingerprints of cases were identical to those of other cases in the risk groups in the previous 2 years.
Measurements and main results: During the study period, 206 individuals with TB among illicit drug users and homeless persons were notified, representing 11.4% of the total case load of 1,811 in Rotterdam. The annual number of tuberculosis cases declined from 24 at the start of the screening program to 11 cases in 2005. The screening program identified 28 cases (a prevalence rate of 327 per 100,000 radiographs), of which 12 were smear positive. In 1997-2002, more than 80% of the illicit drug users or homeless persons with TB were infected with one of the Mycobacterium tuberculosis strains prevalent among these risk groups. After nearly 4 years of systematic radiographic screening this proportion declined to 45% in 2005.
Conclusions: DNA fingerprinting can be a useful tool to evaluate the impact of a TB screening program. We advocate that screening of illicit drug users and homeless persons should be continued to prevent a resurgence of TB.