An additional 33 cases of the Shiga-toxin producing Escherichia coli (STEC) outbreak strain that killed at least 50 people in Germany were reported after it was declared over in July 2011.
Fenugreek sprouted seeds were identified as the most probable source of the E.coli 0104 infections but none of the post-outbreak cases recalled sprout consumption, according to a report in Eurosurveillance.
The outbreak of E. coli O104 was attributed to sprouted seeds from a single producer in Germany .
22 illnesses were confirmed with 17 post-outbreak cases of gastroenteritis, but none of haemolytic uraemic syndrome (HUS), a condition which can lead to kidney failure, and five asymptomatic post-outbreak cases of STEC O104 infection.
The Robert Koch Institute (RKI) coordinated surveillance for ‘post-outbreak’ cases of the infection from 5 July to 31 December 2011.
The goal was to verify the absence of post-outbreak cases associated with sprout consumption and to receive early warning of a potential resurgence.
It also assessed, whether the outbreak strain had managed to establish itself in the German environment, continuing to cause new infections.
“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,” said the report.
The majority were female (20) and adults (26); 19 of 24 symptomatic post-outbreak cases had disease onset from 5 July through 4 September, and five from 5 September to 6 November.
Initial outbreak potency
More than 20% of the recognised outbreak cases developed the life threatening post-diarrhoeal sequela of HUS.
The number of cases of HUS made it the largest known STEC-associated outbreak, said the authors.
Seed sprouts were identified as the source of infection for primary outbreak cases but person-to-person transmission and cases associated with infected food handlers occurred later in the outbreak.
Cases were reported in other countries than Germany, but the majority, as well as most German cases, were associated with residence or temporary stay in the north of Germany.
In France a satellite outbreak occurred in June 2011 attributed to eating fenugreek sprouts. The outbreak peaked on 22 May 2011.
After a lapse of three weeks without newly diagnosed cases, it was declared over after 4 July 2011.
“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”
Authors: C Frank, A Milde-Busch, D Werber