The incidence of VTEC O157 infections is variable throughout the UK with the highest rate in Scotland. The majority of cases of VTEC O157 infection in the UK are apparently sporadic or occur within households.
Outbreaks of VTEC are usually small with an average of 8 cases, however, larger outbreaks can occur. The largest outbreak in England occurred over an eight month period from December 2010 to July 2011. A total of 194 cases were reported in England, with a further 44 cases reported in Scotland and 14 in Wales. Epidemiological investigations suggested there was an association between illness and handling certain loose, raw vegetables. Other large outbreaks have been reported. In Cumbria in 1999, an outbreak associated with pasteurised milk affected 114 people, 88 of whom were laboratory-confirmed. An outbreak in south Wales in 2005 linked to cooked sliced meat comprised 118 microbiologically confirmed cases (of 157 suspected cases). Outbreaks have been documented since 1982, associated with a wide variety of vehicles of infections.
In several countries outbreaks of bloody diarrhoea and HUS have been associated with VTEC belonging to serogroups other than O157, such as the German E. coli O104 outbreak in the summer of 2011 which saw a handful of cases in England, all of whom had travelled to Germany.
In England and Wales, sporadic cases and household incidents have been associated with non-O157 VTEC, but outbreaks have not been described. This is partly due to the lack of methods for the detection of all VTEC that are appropriate for use in diagnostic laboratories. A limited diagnostic service is provided for VTEC of all serogroups by the LGP (see Laboratory ).