onions suspected in North Bay's E. coli outbreak
of Article: http://www.cbc.ca/health/story/2009/06/22/e-coli-north-bay.html
Last Updated: Monday, June 22, 2009 | 3:16 PM ET
North Bay's outbreak was the largest of its kind in
Ontario since seven people died and about 2,500 others fell ill from
water tainted with the same strain in Walkerton, Ont., in May 2000. (CBC)
Contaminated onions were likely behind an outbreak of E. coli at a
fast-food restaurant in North Bay, Ont., that sickened 235 people last
fall, health officials announced Monday.
A Harvey's restaurant was shut down from Oct. 12 to Nov. 12 after health
officials linked it to the outbreak of E. coli O157:H7, which causes
severe abdominal cramping and sometimes bloody diarrhea.
On Monday, health officials with the North Bay Parry Sound District
Health Unit released the findings of their investigation, which concluded
"inconsistent" cleaning could be to blame.
"The epidemiological investigation indicated that this outbreak
was caused by a point source at the Harvey’s restaurant in North Bay,
most likely contaminated onions," the report's authors wrote.
"Although the initial source of the contamination was not
identified, the risk of exposure lingered on-site for about a week.
Inconsistent cleaning of the onion dicer may have perpetuated the
contamination for several days."
The suspected onion could not be confirmed through environmental
testing, food sampling and tests of staff and contacts, said Dr. Jim
Chirico, acting medical officer of health for the North Bay Parry Sound
District Health Unit.
Onion was considered the most likely source of contamination, based
on a statistical analysis comparing what those who fell ill ate versus
controls who did not fall ill.
It is very common that the source is never identified in such
investigations since E. coli symptoms show up one to 10 days (and an
average of three to four days) after the contaminated food is eaten, and
the source is often gone by then.
In this outbreak, exposure to the onions peaked Oct. 5-10 — several
days before people sought medical attention and the health unit learned
of the cases.
No deaths occurred during the outbreak.
Of the 235 people sickened, 93 reported bloody diarrhea, 26 were
hospitalized and one case of hemolytic uremic syndrome (HUS) in a child
HUS is a life-threatening condition that is treated in hospital intensive-care
units. It kills three to five per cent of those afflicted.
Some people who recover may have to contend with lifelong
complications that can include blindness, paralysis and kidney failure.
The investigation spanned 10 health units in Ontario and one other
province, with local, provincial, national and international experts
Chirico noted public awareness of the outbreak seemed to pay off,
since the rate of secondary infections (people infected by others) was
only five per cent, compared with an average of 10 per cent in previous
For future restaurant-based outbreaks, the report's authors
recommended investigating cases among patrons and employees
simultaneously, with stool samples collected from employees as soon the
restaurant is closed to increase the likelihood of identifying infected
They also recommended that:
equipment should be thoroughly cleaned regularly to prevent buildup
safety gloves, which were used at Harvey's, should be avoided or
covered with single-use latex gloves.
steel-mesh gloves can harbour bacteria, they should be cleaned and
with multiple parts should be completely disassembled prior to
a cleaning schedule for the dicer may focus employees' attention on
its proper cleaning.
Consistent application of cleaning policies and procedures is the
issue, said Peter Jekel, the health unit's director of environmental
health, noting Harvey's has been compliant and diligent in adhering to
sanitation practices since the incident.
As for lessons learned from the outbreak, Chirico said it showed why
it's so important for food handlers to stay home when sick and to be
diligent about hygiene and hand washing.
"When you think of how many millions and millions of products
are consumed on a daily basis, and we have not had real explosion of
outbreaks, I think that speaks to the safety system that we do
have," Chirico told a news conference.
North Bay had one confirmed case of E. coli O157:H7 each year between
2005 and 2007.
The report was produced in collaboration with the Public Health
Agency of Canada's Canadian Field Epidemiology Program.