Since 1 December 2010, the HPA Laboratory of Gastrointestinal Pathogens has confirmed and reported 50 human isolates of vero cytotoxin-producing Escherichia coli (VTEC) O157, phage type (PT) 8, expressing genes for Vero Toxin (VT) VT1+2 from laboratories in England and Wales. This compares with an average of 22 cases reported in the same period for the previous three years (10, 16 and 40 cases in 2007/2008, 2008/2009 and 2009/2010 respectively).
Cases are distributed across all regions in England (East (6), East Midlands (1), London (3), North East (2), North West (8), South East (7), South West (6), West Midlands (6), Yorkshire and Humberside (10)) with a single case reported from Wales (figure 1). Sixteen cases (32%) were under 16 years and 15 of these were female; 28 isolates (56%) were from adults aged between 16 and 59 years of which 19 cases (68%) were female. Health Protection Scotland has reported in increase in cases of VTEC O157 PT8 infections during the same time period.
Onset dates, available for 47 cases, suggest a propagated or continuous source for this outbreak (figure 2). Seventeen of the cases became ill in weeks three and four of 2011 (9 to 22 January), with 10 cases reporting illness onset between 14 and 20 January.
Molecular sub-typing by Variable Number Tandem Repeat (VNTR) analysis has been performed on 41 isolates to date; 24 isolates have the same profile and a further seven differ by only a single locus.
An outbreak control team has been convened including members of the Health Protection Agency, the Food Standards Agency, Health Protection Scotland and Public Health Wales. A control study is underway to investigate the source of the outbreak.
Hospital microbiologists are requested to expedite the submission of presumptive E. coli O157 isolates for confirmation and sub typing in order to assist in the investigation of this increase.
Reference
1. Health Protection Scotland. Temporal cluster of E. coli O157 PT8 cases with an indistinguishable subtype, HPS weekly report 09/02/2011 45(6).