a1 New York City Department of Health and Mental Hygiene, Bureau of Tuberculosis Control, New York, NY, USA
a2 Public Health Research Institute, Newark, NJ, USA
a3 Centers for Disease Control and Prevention, Division of Tuberculosis Elimination, Atlanta, GA, USA
a4 Wadsworth Center, New York State Department of Health, Albany, NY, USA
Tuberculosis incidence in New York City (NYC) declined between 1992 and 2000 from 51·1 to 16·6 cases per 100 000 population. In January 2001, universal real-time genotyping of TB cases was implemented in NYC. Isolates from culture-confirmed tuberculosis cases from 2001 to 2003 were genotyped using IS6110 and spoligotype to describe the extent and factors associated with genotype clustering after declining TB incidence. Of 2408 (91·8%) genotyped case isolates, 873 (36·2%) had a pattern indistinguishable from that of another study period case, forming 212 clusters; 248 (28·4%) of the clustered cases had strains believed to have been widely transmitted during the epidemic years in the early 1990s in NYC. An estimated 27·4% (873 minus 212) of the 2408 cases were due to recent infection that progressed to active disease during the study period. Younger age, birth in the United States, homelessness, substance abuse and presence of TB symptoms were independently associated with greater odds of clustering.
(Accepted August 10 2006)
(Online publication October 26 2006)
c1 *Author for correspondence: C. R. Driver, DrPH, RN, New York City Department of Health and Mental Hygiene, Bureau of TB Control, Epidemiology Office, 225 Broadway, 22nd Floor, New York, NY 10007, USA. (Email: firstname.lastname@example.org)