Results of surveillance for infections with Shiga toxin-producing Escherichia coli (STEC) of serotype O104:H4 after the large outbreak in Germany, July to December 2011

After the massive outbreak of infections with Shiga toxin-producing Escherichia coli (STEC) of serotype O104:H4 in Germany in the summer of 2011, post-outbreak surveillance for further infections with this type of STEC was maintained until the end of 2011. This surveillance was based on national mandatory reporting of STEC infections and the associated complication of haemolytic uraemic syndrome (HUS), as well as on data obtained from a questionnaire. Between the outbreak's end (5 July) and 31 December 2011, a total of 33 post-outbreak cases were recorded. Post-outbreak cases occurred with diminishing frequency towards the year's end and resembled the outbreak cases in many respects, however the proportion of HUS among all post-outbreak cases was smaller than during the outbreak. Two thirds of the post-outbreak cases were likely infected by contact with known outbreak cases. Both laboratory and nosocomial spread was noted in this period. No post-outbreak case recalled sprout consumption as a potential source of infection. The scarcity of information conveyed by the nonculture tests routinely used in Germany to diagnose STEC made linkage of post-outbreak cases to the outbreak difficult. Though post-outbreak surveillance demonstrated the outbreak strain's potential for lengthy chains of transmission aided by prolonged shedding, our results and continued routine surveillance until the end of 2013 do not support the notion, that the outbreak strain has been able to establish itself in the German environment. .