Molecular epidemiologic investigation of tuberculosis in an area of increasing incidence in inner-city Dublin.

In 2002 the tuberculosis (TB) incidence in Dublin was 13.1 cases per 100,000 persons. In inner city Dublin, the TB incidence was > 20 per 100,000 persons. TB notification rates have remained elevated. The objective of the study is to characterize the population affected in this inner city area and to investigate transmission patterns and potential risk factors for TB disease. This hospital-based molecular epidemiologic study included all culture positive cases of TB between January 1, 1998 and December 31, 2002 from the Mater Misericordiae University Hospital. 142 cases were analyzed. 84 (59%) had clustered Mycobacterium tuberculosis (Mtb) isolates, 58 (41%) had unique isolates by molecular typing. There were 13 clusters; the largest two clusters had 26 cases each, one linked to pubs, the other linked through family contact. In multivariate logistic regression analysis, birth in Ireland, pulmonary TB, and younger age were significantly associated with recent transmission. Dublin is a developed city with persistent areas of high rates of TB in the native population. Despite a functioning public health system and lack of predisposing risk factors such as HIV, immigration, and extreme poverty, TB can persist in pockets of the younger, native population.