E. coli O157, lettuce - Sweden (West Coast) 2005

International Society for Infectious Diseases
<http://www.isid.org>

In response to E. coli VTEC non-O157, lettuce - USA (UT)
[20060904.2521] where there were discussions about how the lettuce
had become contaminated:

During late summer 2005, the largest outbreak of EHEC
[Enterohemorrhagic _E. coli_ ] O157 ever recorded in humans in any
Nordic country occurred in Sweden. There were 135 cases recorded, of
these 11 patients developed hemolytic uremic syndrome. There were no
fatal outcomes.

Epidemiological investigations implicated lettuce as the source of
the outbreak. Water samples taken from a small stream used for
irrigation of lettuce were positive for O157 VT 2 [Vero toxin 2 -
Mod.LL] by PCR [polymerase chain reaction]. A strain identical to
that found in the human cases was also isolated from cattle of a
nearby farm, upstream the irrigation point. We were not able to
isolate the EHEC strain from lettuce.

This outbreak will be presented as an poster at the VTEC 2006
Congress in Melbourne, Australia.

--
Ann Soderstrom MD PhD
Department of Communicable Disease Control
Vastra Gotaland, Sweden

Yvonne Andersson
Head Epidemiologist
Swedish Institute for Infectious Disease Control

Anders Lindberg MD National Board of Health and Welfare
Sweden

Aspects of this outbreak had been posted on ProMED
previously (see below), and this update gives the final case count
and identifies the source. It will be interesting to see if the USA
outbreak is also traced to cattle.

A map of Sweden showing the location of the affected area, Vastra
Gotaland in the southwestern part of the country, can be found at:
< http://content.answers.com/main/content/wp/en-commons/thumb/c/c7/120px-Svcmap_vastra_gotaland.png>