Transmission of mycobacterium tuberculosis depending on the age and sex ofsource cases

This study estimated to what extent tuberculosis transmission in the Nether lands depends on the age and sex of source cases. DNA fingerprints of Mycob acterium tuberculosis isolates were matched to patient information in the N etherlands Tuberculosis Register for 1993-1998. Clusters were defined as gr oups of patients with pulmonary tuberculosis whose isolates had identical D NA fingerprints. Source cases were assigned by using two models. The first- case model assumed that the first diagnosed case was the source case. The i ncidence rate model estimated source case probabilities from the incidence rates of potential source cases and the time of diagnosis. DNA fingerprints of 6,102 isolates were matched to patient information on 5,080 (83%) cases , 3,479 of whom had pulmonary disease. According to both models, the number of infectious cases generated per source case was lower for female than fo r male source cases and decreased with increasing age of the source case. T he authors concluded that transmission of tuberculosis is associated with t he age and sex of source cases as well as the age of secondary cases. Incre ased transmission among immigrant groups in the Netherlands is largely attr ibutable to the relatively young age of immigrant source cases.