Published Date: 2011-10-01 23:17:50
Subject: PRO/AH/EDR> E. coli O157 - UK (03): leeks, potatoes
Archive Number: 20111001.2965
E. COLI O157 - UNITED KINGDOM (03): LEEKS, POTATOES
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Fri 30 Sep 2011
Source: The Guardian [edited]
An 8 month _E. coli_ O157 outbreak across the UK left 250 people ill
and one dead, but was not publicized at the time because its origins
were unknown, health officials say. After 6 months of investigations
the infection was ultimately linked to people handling loose raw leeks
and potatoes in their homes, said the Health Protection Agency (HPA),
which has only now acknowledged the outbreak.
The cases began in December 2010 and continued until July 2011. In
total 250 victims, 100 of them under 16, were left sick with vomiting
and diarrhea. Of those, 74 needed hospital treatment, including 4 who
developed hemolytic-uremic syndrome which can lead to kidney failure.
One unnamed patient, who the HPA said had underlying health problems,
The outbreak involved a rare strain of _E. coli_ 0157 called Phage
Type 8 (PT8). It affected 193 people in England, 44 in Scotland and 14
in Wales. While 40 percent of the 250 were under 16 years old, 69
percent were female. In each of the past 3 years an average of 81
people across the UK have been infected with _E. coli_ 0157 PT8.
The HPA said, Health Protection Scotland and Public Health Wales began
becoming aware of increased numbers of _E. coli_ cases from December
2010 onwards. An initial inquiry, which asked all those affected about
their food intake and places they had visited, proved inconclusive.
Unlike other _E. coli_ outbreaks it was not possible to identify a
single source for the outbreak, such as a commercial or children's
farm, or food producer.
It was only after a 2nd round of in-depth interviews with 30 sufferers
that investigators realized that victims were 40 times more likely to
have been in a home where people handled leeks sold loose and 12 times
more likely to have been in a household where potatoes were bought in
or sold from sacks had been handled, compared with a control group of
62 unaffected people.
"Our study showed a statistically significant association with raw
loose leeks and potatoes from sacks, but these vegetables may not be
the only source of contamination," said Dr Bob Adak, an HPA
gastrointestinal expert who led the multi-agency outbreak control team
that investigated it. Soil on the vegetables is thought to have been
the likely source of the _E. coli_ bacteria. "In this outbreak, which
is now over, the vegetables could have carried traces of contaminated
soil. It is possible people caught the infection from
cross-contamination in storage, inadequate washing of loose
vegetables, insufficient hand washing after handling the vegetables or
by failing to thoroughly clean kitchen equipment, utensils or surfaces
after preparing the vegetables."
A spokeswoman said the HPA did not alert the public to the ongoing
outbreak because they did not know where it had originated and
therefore could offer no useful public health advice. "At the outset
it was not clear what was causing the outbreak and we had no
information that would have enabled the public to take any steps to
protect themselves," she said. "It was only following extensive and
complex epidemiological investigations and analysis that a cause
"Although the outbreak is over, we feel it is still important to share
our findings with the public so that they can take the appropriate
action to guard against any possible recurrence.
"As the number of new cases had declined significantly by June 2011,
and there was not an immediate need to issue a health alert to the
public, we waited until FSA's customary consultation processes with
industry and consumer organizations were completed before making this
"During the upcoming autumn and winter months, people are more likely
to be using these types of vegetable in their cooking, so it was also
decided that now was the right time to make this information public."
Dr Andrew Wadge, chief scientist at the Food Standards Agency (FSA),
which was also involved in the outbreak control team, said: "It's
sadly a myth that a little bit of dirt doesn't do you any harm; soil
can sometimes carry harmful bacteria and, although food producers have
good systems in place to clean vegetables, the risk can never be
entirely eliminated. Control of infection from _E. coli_ O157 relies
on an awareness of all potential sources of the bacteria and high
standards of hygiene where it may be present.
"This outbreak is a timely reminder that it is essential to wash all
fruits and vegetables, including salad, before you eat them, unless
they are labeled 'ready to eat,' to ensure that they are clean. It is
also important to wash hands thoroughly as well as to clean chopping
boards, knives and other utensils after preparing vegetables to
prevent cross contamination," Wadge added.
[Byline: Denis Campbell]
ProMED-mail Rapporteur Mary Marshall
[There is no information regarding what investigations were done to
track backwards in assessing from where the epidemiologically linked
foods were grown and/or processed related to this substantial
outbreak. It is also quite possible that the produce was shipped
outside of the UK proper. - Mod.LL]