Factors associated with the high tuberculosis case rate in an urban area

SETTING: The Rotterdam region, the Netherlands, 1995-2006. OBJECTIVE: To identify factors associated with the high tuberculosis (TB) case rate in an urban area. DESIGN: Municipalities were divided into urban and semi-urban/rural municipalities. We compared the characteristics of TB cases and stratified case rates according to age group, immigrant status and place and time of infection between the two areas. RESULTS: The TB case rate in urban municipalities was 3.8-fold higher than in semi-urban/rural municipalities. After stratification for country of birth, the rate ratios were lower (1.7 for immigrants and 2.8 for non-immigrants). Immigrants had most frequently acquired their infection abroad (47% of urban and 62% of semi-urban/rural immigrant cases). In 40% of urban cases and 27% of semi-urban/rural cases, the infection was recently acquired in the Netherlands, translating into a 5.7-fold higher recent transmission case rate for the urban population. CONCLUSIONS: The high urban TB case rate was related to the high proportion of urban immigrants who frequently reactivated an infection acquired abroad. Recent transmission also contributed to a substantial part of the TB caseload in urban municipalities among both urban immigrants and non-immigrants. The authors propose a package of targeted interventions to address the identified factors associated with the high urban TB case rate.