P50 A summary of strain typing and clustering of TB in London in 2010 and an analysis of the associated risk factors

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Since January 2010 prospective strain typing on all positive TB samples able to be cultured has occurred. Recent infection is presumed if the strain of TB isolated from the case is indistinguishable from one or more others in the population studied. Recently infected cases are likely to be part of clusters. All data are currently preliminary. In London from January to September 2010, 2679 cases were reported to the London TB Register, 36% of which were culture confirmed. Of those that were culture confirmed 37% were in a cluster. Adults were more likely to be culture confirmed than children (37% vs 23%). While children may be less likely to be culture confirmed, those who were culture confirmed were more likely to be clustered (and so recently infected). Comparing children (0–15 year olds) to young adults (16–24 year olds), 70% compared to 40% were clustered (OR 3.49, p=0.003). Overall more clustering was noted among males (39% vs 33%, OR 1.28, p=0.08), white (40%) and black-Caribbean (47%) ethnic groups, UK born cases (42% vs 36%), and those with pulmonary (45% vs 30%) and sputum smear positive disease (56% vs 38%). More clustering was seen with those who had social risk factors: history of drug use (46%), homelessness (49%), imprisonment (47%), and alcohol abuse (46%). The majority were in clusters with <5 cases and therefore did not reach the HPA cluster investigation threshold of =5 cases in 24 months. Data will be presented for the entirety of 2010, therefore numbers are subject to change.

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