Embed Size (px)
Citation preview
1
OUTBREAK CONTROL TEAM REPORT ON THE OUTBREAK OF E. COLI 0157
AT NEW DEER MILLENNIUM SCOUT CAMP MAY/JUNE 2000
November 2000
Dr Arun Mukerjee, Consultant in Public Health Medicine (CD&EH), Grampian Health Board
Dr Helen Howie, Senior Registrar in Public Health Medicine, Grampian Health Board Colin Houston, Principal Environmental Health Officer, Aberdeenshire Council Jayne Leith, CD Nurse, Grampian Health Board
On behalf of the Outbreak Control Team
2
TABLE OF CONTENTS
Chapter Subject Page No
Summary & Recommendations 1 1 Introduction 2 2 E. coli O157 3 3 The Scout Camp 4 4 Control Measures
4.1 Outbreak Control Team 4.2 Identification and removal of risk at
source 4.3 Case definition 4.4 Ascertainment of cases 4.5 Exclusion of cases 4.6 Education 4.7 Counselling of contacts 4.8 Interim guidance – Avoiding ill health
at Camp
5 5 5 5 5 6 6 6
5 Epidemiological Investigation 5.1 Data collection methods 5.2 Definition of a camp attendee 5.3 Camp attendees 5.4 Age, sex and scout district 5.5 Prevalence of gastro-intestinal illness
in the community 5.6 Reported symptoms in attendees 5.7 Chronology of incidence of cases of
E. coli O157 5.8 Attack rate by age group, sex and
scout district 5.9 Camp activities as risk factors for the
transmission of E. coli O157
7 7 7 8 8 8 8
10
11 7 Environmental Investigation
7.1 Environmental samples 7.2 Food and Water samples 7.3 Sanitary Facilities
13 13 13
8 Microbiological Investigations 8.1 Human microbiological results 8.2 Individuals with Diarrhoea 8.3 Individuals with vomiting only 8.4 Veterinary microbiological results 8.5 Food & Water results 8.6 Environmental Samples 8.7 Typing of isolates
14 14 14 14 14 15 15
9 Communication 9.1 Parents of children attending the
camp and all adult attendees 9.2 General Practitioners 9.3 Education Department 9.4 Press 9.5 Other Professionals
16 16 16 16 16 16
10 Conclusions and Recommendations 17
3
References 18
Appendix 1 Membership of Outbreak Control Team 19
Appendix 2 Enteric Disease Surveillance Form 20 Appendix 3 Map of Aberdeenshire 28 Appendix 4 Map of the Camp Site 29 Appendix 5 Exclusion Criteria
i) Dated 6th June 2000
ii) Dated 15th June 2000
30 31
Appendix 6 Interim Guidance “Avoiding ill health at Camp”
32
Appendix 7 Questionnaire 1 34 Appendix 8 Questionnaire 2 38 Appendix 9 Letters to Parents
i) Dated 4th June
ii) Dated 7th June
iii) Dated 13th June
39 40 41
Appendix 10 Letters to General Practitioners i) Dated 5
th June
ii) Dated 6th June
42 43
Appendix 11 Letter to Education Authority i) Dated 6
th June
ii) Dated 16th June
iii) Dated 20th June
44 45 46
Appendix 12 Press Releases issued by Grampian Health Board
47
4
Summary & Recommendations In May 2000 a Scout Camp was held at New Deer Agricultural Showground in Aberdeenshire as part of the Millennium celebrations. The camp was attended by 337 people. This included 233 cubs, scouts and venture scouts plus 104 leaders and other helpers. The camp was abandoned early because of the atrocious weather conditions. 20 attendees were later confirmed as having E. coli O157 with dates of onset suggestive of a point source outbreak. In addition another 50 reported gastrointestinal symptoms. On 4
th June an outbreak control team was convened to control and investigate the outbreak. A
descriptive and analytical epidemiological investigation was undertaken. Extensive microbiological and environmental sampling was carried out which included samples of sheep faeces, lying water, food, drinking water, mud, soil and debris from climbing equipment. E. coli O157 was isolated from the sheep faeces, lying water, soil, Wellington boots and debris from the climbing frame. The animal, environmental and human isolates of E. coli O157 were indistinguishable on pulse-field gel electrophoresis. The weather conditions during the camp were very poor with heavy rain. The camp was held on ground previously used for grazing sheep and it was reported that it was heavily contaminated by sheep faeces. The heavy rainfall caused localised flooding and very muddy conditions. It was postulated that the likely route of transmission for E. coli O157 was via hands contaminated with mud before eating food or direct from hands to mouth. Although hand-washing facilities were available many of the camp attendees did not wash their hands. The analytical epidemiological investigation showed that the camp attendees who did not use cutlery or washed their hands were 7-9 times more likely to be ill with E. coli O157 than those who did. Climbing the tower and eating at the barbecue also increased their chances of becoming unwell. This supports the hypothesis that environmental contamination of hands or food was the most likely route of infection and suggests that there is a protective effect from washing hands and using cutlery to minimise the risk of environmental contamination of hands or food. Microbiological, environmental and epidemiological investigations confirmed that the environment was the most likely source of infection. As a result of this outbreak the Scout Association and Aberdeenshire Council have prepared interim guidance on “Avoiding ill health at camp” to supplement the Scout Association’s existing guidance on “Scout Camping” and “Food Safety – The Preparation and Storage of Food” RECOMMENDATIONS 1. Revised guidance on appropriate selection, preparation and management of sites should
be available to organisations proposing to hold any type of activity (e.g. camping, caravanning, agricultural shows, fairs etc) on land normally used for the grazing of animals.
2. Guidance on appropriate selection, preparation and management of sites should be
available to organisations proposing to hold any type of activity involving agricultural animals on public land not normally used for agricultural purposes e.g. agricultural shows on public land.
3. Further research is required to investigate the animal reservoir and carriage of E. coli
O157 and survival of the organism in the environment.
5
Introduction Chapter 1
On 1
st June 2000 an eight-year-old boy was admitted to the Royal Aberdeen Children’s Hospital
(RACH) with gastro-enteritis. On 2nd
June Grampian Health Board’s (GHB) Communicable Disease Team was notified that E.coli O157 had been isolated from faecal samples from this child. The parents were interviewed on 2
nd June and the GHB enteric surveillance form was
completed (Appendix 1). During the course of the interview the parents confirmed that he had attended the Millennium Scout Camp held at the New Deer Agricultural Show Ground in Aberdeenshire on the 26
th and 27
th May 2000 and that two other children possibly had similar
symptoms. It was reported that over 300 people attended the camp. As a precaution the Scout Association was contacted on the 2
nd June and asked to compile a list of names, dates of birth
and addresses of those who attended the camp. The Specialist Environmental Health Officer (Food), Aberdeenshire Council was fully informed of the situation on 2
nd June.
On 4
th June the Public Health on call doctor was informed that a second child had been admitted
to RACH with a probable diagnosis of E. coli O157. During the interview with the family other camp attendees were reported as being unwell, including an adolescent who had been admitted to the Infection Unit at Grampian University Hospital Trust (GUHT) with symptoms suggestive of E. coli O157. Both cases had attended the Millennium Scout Camp at New Deer. The camp organisers reported that more than 30-40 children had become ill with gastrointestinal symptoms since the camp. Many complained of diarrhoea and/or vomiting of short duration and were now well. On the 4
th June an outbreak of gastrointestinal disease was declared and an Outbreak Control
Team (OCT) was convened at 6pm in compliance with the guidance of Scottish Executive Health Department (1999).1 See Appendix 2 for membership of OCT. The OCT reviewed the information available to date and agreed additional investigations, control measures and advice to parents, GPs and the media.
6
Chapter 2 E. coli O157
Escherichia coli (E. coli) bacteria are found in the digestive tracts of most humans and animals. There are hundreds of different strains of E. coli and usually these bacteria are harmless.
2
Some strains of E. coli produce toxins and are known as Vero cytotoxin producing E. coli (VTEC). E. coli O157:H7 is a particular strain that can cause serious illness in humans. These bacteria are capable of invading the gut and can produce a toxin that may affect the kidneys leading to haemolytic uraemic syndrome (HUS). E. coli O157:H7 can be further sub-typed to assist in epidemiological investigation of outbreaks. Over 15% of healthy cattle and 2% of sheep may carry E. coli O157 in their gut.
3 Animals are
usually unaffected by E. coli O157. However a small number may become ill. Animal faeces contaminated with E. coli O157 may in turn contaminate water and soil. It is, at present, unknown how long E. coli O157 can survive in particular environments but research indicates that it can survive in soil for several weeks.
3
E. coli O157 can be transmitted to humans in a variety of ways including eating under cooked meat that is already infected, consuming unpasteurised milk or milk products or contaminated water. Transmission can also occur through inadequate hygiene after contact with contaminated soil. Person to person transmission can occur by faecal-oral route. Inadequate hand hygiene following contact with any of these vehicles can lead to the ingestion of the bacteria. E. coli O157 needs very few bacteria to cause infection in a susceptible individual. The incubation period for E. coli O157 varies between 1 and 14 days but is usually 3-4 days. The symptoms caused by E. coli O157 can vary considerably depending on how the individual reacts to the organism. The individual may be asymptomatic, but is more likely to have stomach cramps and diarrhoea. This may resolve but occasionally the disease progresses to the next stage when the diarrhoea becomes bloody. A small number of individuals may develop more serious complications including kidney failure as a result of HUS. The disease tends to be more serious in young children and the elderly.
7
Chapter 3 The Scout Camp
As part of the Millennium celebrations the Scout Association held a camp at New Deer Agricultural Show Ground in Aberdeenshire. Fourteen cub and scout groups representing the three districts of North East Aberdeenshire attended the camp. The camp attendees came from the communities shown on the map in Appendix 3. This map also shows the location of the campground at New Deer. Attendees did not belong to any other common social network and attended schools and leisure facilities local to their district. Camp organisers reported that sheep had been grazing on the New Deer Agricultural Show Ground until Thursday 25
th May. Consequently there was no time to cut the grass as initially
intended and the ground was heavily contaminated with sheep faeces. It was established later that around 200 sheep had been grazing on the field. Scout Leaders and volunteers assembled the camp on Thursday 25
th May. It was originally intended to camp from Friday 26
th until Sunday
28th May however it was abandoned on Saturday 27
th because of poor weather conditions. Video
footage shows that certain areas of the show ground were water logged by Saturday 27th May.
(Appendix 4 for a plan of the campsite). Each group had their own sleeping tents. The menus and the purchase of food were organised by the individual group leaders. Food was cooked and eaten in the groups’ own dining shelter, trailer or mess tent or in shared mess tents. On Saturday evening several groups cooked their food on barbecues. Drinking water was supplied by standpipes connected to mains water supply. A bowser was also provided to supply additional water. This had been cleaned and disinfected prior to use and filled with mains water. Toilets with hand washing facilities were located at convenient sites around the camp (Appendix 4). Various outdoor activities took place at the camp including the preparation and consumption of bread doughsticks cooked over a barbecue. One of the groups assembled a Pioneer Tower that was climbed by many of the children and some adults.
8
Chapter 4 Control Measures
4.1 Outbreak Control team
On 4th June an OCT was convened and subsequently met five times. The team was
stood down on the 21st June. (Appendix 1 for details of OCT).
4.2 Identification and removal of risk at source
On 4th June it was not clear if this was a foodborne outbreak and the Scout leaders were
asked to ensure that no food remaining from the scout camp was used at any other event.
On 4
th June the New Deer Agricultural Association were contacted and asked to ensure
that no further camping took place on the field until preliminary investigations were complete. This was a precautionary measure to protect any other campers from a similar exposure
4.3 Case definition
A ‘case’ was defined as any individual who had attended the New Deer camp on 26th or
27th May and who developed abdominal pain and/or diarrhoea with a positive faecal
culture for E. coli O157 within 14 days of the camp. 4.4 Ascertainment of cases
• Notification of confirmed cases of E. coli O157 by the microbiology laboratory at Grampian University Hospitals Trust (GUHT).
• On 4th June all individuals reported as unwell by the cases or their families were contacted. Those with diarrhoea were advised to submit stool samples.
• On 4th June the scout leaders provided a list of the ill children known to them at that time.
On 5th June all individuals identified by the scout leaders were contacted by telephone
and if their symptoms included diarrhoea they were asked to submit a faecal sample.
• On 4th June the out of hours GP co-operatives, G-DOCS and Moray-Docs, and Dr Gray’s
Hospital in Elgin were alerted to the situation.
• On 4th June, following the first OCT meeting, a questionnaire was prepared and sent to all
those who attended the camp or their parents. All respondents whose symptoms included diarrhoea and had not been previously contacted by the Communicable Disease Team (CD team) were interviewed by telephone and asked to submit a faecal sample.
• On 7th June all camp attendees whose only symptom was vomiting were also asked to
submit a faecal sample as the clinical history in some of the attendees was strongly suggestive of a viral infection.
4.5 Exclusion of cases
It is routine practice in Grampian to screen all household contacts of cases of E. coli O157 and to identify all those in the high risk groups A-D.
9
Table 1. Groups posing a special risk of spreading infection4
A Any person of doubtful hygiene or with unsatisfactory toilet or hand drying facilities at
home, work or school.
B Children who attend pre-school groups or nursery
C People whose work involves preparing or serving unwrapped foods not subject to further heating or cooking.
D Health or social care staff who have direct contact with highly susceptible patients or persons in whom a gastrointestinal infection would have a particularly serious consequence.
Initial advice to any symptomatic individual was to remain off work/school until 48 hours symptom free, seek advice from their GP and practice meticulous hand hygiene. All GP’s were advised to submit samples from camp attendees who presented with diarrhoeal symptoms. (See Appendix 5 for exclusion policies).
In an outbreak the OCT can impose stricter exclusion policies to minimise spread of infection.1 On 6
th June the initial advice was revised and agreed by the OCT on the 7
th
June. All children known to have had diarrhoea were excluded from school until they had submitted one negative sample. Children whose only symptom was vomiting were advised to remain off school until 48 hours symptom free and practice meticulous hand hygiene on return to school.
Adults with diarrhoea were asked to submit a faecal sample for examination. All symptomatic adults were advised to stay off work until 48 hours symptom free and practice meticulous hand hygiene on return to work.
All E. coli O157 positive individuals were excluded from school or work until they had submitted two consecutive negative faecal specimens twenty-four hours apart. Symptomatic contacts of positive cases were asked to remain at home until the results of their faecal sample tests were available. Contacts of positive cases in all high-risk groups were excluded from school/work until they had two negative stool samples in accordance with national guidance.
1
On 15
th June this exclusion policy was relaxed. From this date secondary school children
who were positive for E. coli O157 were allowed to attend school as long as they were 48 hours symptom free, practised meticulous hand hygiene and did not participate in any food preparation at school. (Appendix 5)
4.6 Education
The CD Team recommended that hand hygiene was promoted and that sufficient soap and hand-drying facilities were available. Schools were informed about the exclusion of symptomatic children and all household contacts were screened for infection.
4.7 Counselling of contacts
All children and adults known to have had symptoms who were telephoned by the CD Team were given infection control advice. All parents of positive cases were contacted by the CD Team and advised on the prevention of secondary spread.
4.8 Interim guidance - Avoiding ill health at Camp
The Environmental Health Services of Aberdeenshire Council advised the Scout Association on the preparation of interim guidance on “Avoiding ill health at Camp”. The Scout Association Scottish Council has issued this interim guidance widely within the Scout Association. (Appendix 6)
10
Chapter 5 Epidemiological Investigation
5.1 Data collection methods
Data were collected from the initial cases using the standard GHB enteric surveillance form (Appendix 2). Two self-complete questionnaires were sent out to the camp attendees as part of the epidemiological investigation. The Scout leaders distributed Questionnaire 1 on the evening of the 4th June. This was an amended enteric surveillance form with some additional questions to ascertain possible risk factors. The response rate was 86%. (Appendix 7) Questionnaire 2 was sent out on 13
th June to test
a range of hypotheses as to the likely vehicle of transmission. The response rate to this second questionnaire was 78%. (Appendix 8)
5.2 Definition of a camp attendee
A ‘camp attendee’ was defined as anyone who attended the camp and stayed overnight or participated in any of the activities or who had eaten any food at the camp. 372 people were notified to the CD Team as attending the camp but this included 35 who had attended to drop off children or to erect or dismantle tents etc and are excluded from any further analysis. 337 people fulfilled the definition of camp attendee.
5.3 Camp attendees
There were three districts represented at the Millennium Camp with 14 groups of scouts or cubs. Some groups consisted of more than one unit. See Table 2 below for description of camp attendees.
Table 2. Camp attendees by scout district and group
District and group Cub Scout Venture
scout Leader Others* Total
Banff District
Banff 8 - - 5 - 13
Cornhill 5 - - 3 2 10
Macduff - 22 - 5 1 28
Portsoy and Fordyce 12 11 - 5 3 31
Whitehills 11 - - 2 - 13
Buchan District
Fraserburgh 23 18 1 6 13 61
Maud 8 - - 3 2 13
Peterhead and Longside 18 16 - 7 2 43
RAF Buchan 14 - - 4 - 18
Ugie 15 - - 1 - 16
Turriff District
Fyvie 2 7 - 3 4 16
Fyvie Venture Scouts - - 10 3 - 13
Rothienorman - 8 - 3 - 11
Turriff 15 9 - 11 - 35
Not allocated to a District - - - 1 15 16
Total camp attendees 131 (39%)
91 (27%)
11 (3%)
62 (18%)
42 (12%)
337
*Others include helpers, visitors, administrators and St Andrew’s Ambulance Staff
11
5.4 Age, sex and scout district
Table 3 shows the camp attendees by age sex and district. The age groups were used to correlate with the cubs (8-11yrs), scouts (12-16yrs) and venture scouts (17-25yrs). The age groups do not match exactly as time of transfer between units can vary. 69% (233/337) of camp attendees were cubs, scouts or venture scouts. The majority of camp attendees were male 88% (297/337) and 12% (40/337) were female. 45% were from Buchan District, 28% from Banff District and 22% from Turriff District. Over 40% of the attendees were aged 8-11 years.
Table 3. Age and sex of the attendees and their proportion in each age group by district of residence.
Sex Scout District Age
Group (years)
Total Number Male Female Banff Buchan Turriff No
district
N N (%) N (%) N (%) N (%) N (%) N (%)
8-11 147 (44%)
147 (100%)
0 39 (27%)
85 (58%)
21 (14%)
2 (1%)
12-16 81 (24%)
75 ( 93%)
6 (7%)
29 (36%)
29 (36%)
23 (28%)
0
17-25 24 (7%)
15 (63%)
9 (38%)
4 (17%)
6 (25%)
12 (50%)
2 (8%)
>25 84 (25%)
60 (71%)
24 (29%)
23 (27%)
31 (37%)
19 (23%)
11 (13%)
Total 337 (100%)
297 (88%)
40 (12%)
95 (28%)
151 (45%)
75 (22%)
15 (4%)
N = number. % = percentage of each age group
5.5 Prevalence of gastro-intestinal illness in the community
In the GHB area the most common bacteria that causes enteric illness is campylobacter. Less commonly cryptosporidia, salmonella and E. coli O157 cause enteric illness. There had been no unexpected increase in the numbers of enteric illness, especially cases of E. coli O157, isolated in Grampian within the two months prior to the date of commencement of the camp. There was no known association between any of the sporadic cases of E. coli O157 in the community and the New Deer Camp attendees.
5.6 Reported symptoms in attendees
70 respondents complained of gastrointestinal symptoms including diarrhoea and/or vomiting. 48 respondents complained of diarrhoea and 35 complained of vomiting. These are not mutually exclusive as some people complained of both diarrhoea and vomiting. E. coli O157 was isolated from only 20 (29%) of the symptomatic respondents. 18 individuals from one scout camp reported symptoms suggestive of a viral infection i.e. short episodes of vomiting only.
5.7 Chronology of incidence of cases of E. coli O157
Between the 2nd
and 16th June 20 camp attendees were notified as E. coli O157 positive.
Figure 1 shows the epidemic curve by date of onset of symptoms. The illness was characterised by abdominal pain (25%), diarrhoea (100%) of which (25%) was bloody. Unusually vomiting was noted as a symptom in 25% of the cases. One child developed haemolytic uraemic syndrome (HUS) and required dialysis. All the cases recovered.
12
Figure 1 Epidemic curve of cases of E. coli O157 by date of onset. Table 4. Date of Onset of Symptoms, Date Notified and District
Case number Date of onset of symptoms
Date Notified District
1 28-May-00 8-Jun-00 Turriff
2 28-May-00 7-Jun-00 Turriff
3 29-May-00 15-Jun-00 Banff
4 29-May-00 2-Jun-00 Banff
5 30-May-00 7-Jun-00 Banff
6 30-May-00 5-Jun-00 Banff
7 30-May-00 9-Jun-00 Banff
8 30-May-00 5-Jun-00 Banff
9 30-May-00 8-Jun-00 Banff
10 30-May-00 5-Jun-00 Banff
11 30-May-00 15-June-00 Turriff
12 31-May-00 9-Jun-00 Turriff
13 31-May-00 9-Jun-00 Banff
14 31-May-00 9-Jun-00 Turriff
15 31-May-00 8-Jun-00 Banff
16 1-Jun-00 5-Jun-00 Banff
17 1-Jun-00 9-Jun-00 Turriff
18 1-Jun-00 8-Jun-00 Buchan
19 2-Jun-00 5-Jun-00 Banff
20 3-Jun-00 9-Jun-00 Banff
0
1
2
3
4
5
6
7
8
28/05/00 29/05/00 30/05/00 31/05/00 01/06/00 02/06/00 03/06/00
Date of Onset
No
s o
f c
as
es
13
5.8 Attack rate by age group, sex and scout district.
Table 5 below shows the number of camp attendees who were confirmed with E. coli O157 by age group and scout district and the attack rate. No one over the age of 25 became ill with E. coli O157. A higher proportion of individuals from Banff District (14%) were ill than in the Buchan (0.6%) and Turriff (8%) and this was consistent within age groups. When the attack rates between age groups for all districts were compared no difference was noted. Although 58% of the 8-11 year age group were from the Buchan District the overall attack rate for the district was only 0.6% compared to Banff where only 27% of the attendees were aged 8-11 years with an attack rate as high as 14%. Male attendees outnumbered females by 7:1 but there was no significant difference in attack rates between the two sexes, 6% in males and 8% in females. These findings pointed to the need to look for other risk factors for the transmission of E. coli O157.
Table 5. Attack rates by age groups and scout district
Attack rate by Scout District
Banff Buchan Turiff All
Age Group
Number Number ill (AR)
Number Number ill (AR)
Number Number ill (AR)
Number Number ill (AR)
8 – 11
39 7 (18%)
85 1 (1%)
21 3 (14%) 145 11 (8%)
12 – 16
29 5 (17%)
29 0 23 2 (9%)
81 7 (9%)
17 – 25
4 1 (25%)
6 0 12 1 (8%)
22 2 (9%)
26+
23 0 31 0 19 0 73 0
Total
95 13 (14%)
151 1 (0.6%)
75 6 (8%)
321 20 (6%)
Number ill = confirmed E. coli O157 AR = attack rate of coli O157 by age group and district. Note: 16 camp attendees were not allocated to a District and included 2 in age group 8-11 and 2 in 17-25.
Figure 2 Num ber of cases by district and age group
Scout district
B anff D istrictBuchan D istrictTurriff D istrict
Nu
mb
er
of
ca
se
s
14
12
10
8
6
4
2
0
AG EG R O UP
17-25
12-16
8-11
14
5.9 Camp activities as risk factors for the transmission of E. coli O157
E. coli O157 was isolated from the sheep faeces and the surface water at the camp site and therefore it was considered likely that the source of infection was environmental contamination of food or hands prior to eating. Discussion with the camp organisers identified a number of activities that may have increased the likelihood of the children acquiring E. coli O157. These included:
� Eating food prepared at a camp barbecue � Eating doughsticks prepared at the camp � Climbing the tower � Not washing hands before barbecues � Not washing hands before meals � Not using knives and forks
These risk factors were further investigated by the second questionnaire. The response rate was 78% (263/337). The results are shown as a proportion of the number who replied to the question and therefore the totals will vary. Missing data are not included in the analyses.
Table 6. Attack rate for E. coli O157 by activities
Participated Did not participate
ill Total Attack rate %
ill Total Attack rate %
Relative Risk
95% CI*
Ate at a BBQ 10 77 13% 10 186 5.4% 2.42 1.05-5.57
Did not wash hands before BBQ
8
35
23%
2
41
5%
4.69
1.06-20.63
Did not wash hands before meals
17
162
10%
1
85
1%
8.92
1.21-65.89
Did not use knives and forks at meals
17
169
10%
1
75
1%
7.54
1.02-55.66
Ate doughsticks 7 65 11% 11 189 6% 1.85 0.75-4.57
Climbed tower 11 89 12% 7 162 4% 2.86 1.15-7.12
*95% CI - 95% confidence that the true results lie within the range of results given.
The relative risk quantifies how many more times individuals exposed to the risk factor are likely to develop a disease than those who are not exposed.
Those camp attendees who did not wash their hands before meals were nearly 9 times more likely to be ill with E. coli O157 than those who did wash their hands. Those who did not use cutlery for their meals were 7 times more likely to become ill than those who did use cutlery. The confidence intervals are very wide for both these relative risks probably due to the very small numbers in some of the groups. Climbing the tower and eating at the barbecue increased the likelihood of becoming ill with E. coli O157 and this also supports the hypothesis that environmental contamination of hands or food was the likely route of infection.
15
Table 7. Number of respondents who participated in the activities by district Banff Buchan Turriff
Activities Total N (% ) Total N (%) Total N (%)
Ate at barbecue 76 56 (74%)
117 17 (15%)
75 4 (5%)
Washed hands before barbecue
55 27 (50%)
17 12 (70%)
4 2 (50%)
Always washed hands before meals
76 22 (29%)
109 41 (38%)
58 20 (35%)
Always used knives and forks
76 18 (24%)
108 33 (31%)
56 23 (31%)
Ate doughsticks 76 27 (35%)
111 24 (22%)
59 11 (19%)
Climbed tower 76 39 (51%)
107 17 (16%)
59 29 (49%)
A higher proportion of attendees from Banff district participated in activities that were more likely to increase their exposure to environmental contamination prior to eating and were less likely to wash their hands or use knives and forks. This may explain the higher attack rate of E. coli O157 in Banff District. The only association between activities and becoming ill that remained significant when analysed by districts was the association between becoming ill and not washing hands before meals in the Banff District. Although the association of becoming ill with eating dough sticks was not significant when analysed by district 35% of attendees from Banff District ate doughsticks compared to 19% and 22% for Turriff and Buchan respectively. Table 8. Number of attendees who always washed hands before meals and their proportion by age groups
Age group
Total Always washed Hands
% washed*
8-11 years 111 24 21%
12-16 years 63 18 28%
17-25 years 19 8 42%
>25 54 35 65%
* significant difference between age group and washing hands Chi square test with 3 degrees of freedom.
There was a highly significant association found between age group of camp attendee and whether they always washed their hands. The likelihood of washing their hands increased with age. However the attack rate for all age groups under 25 was similar – see Table 5. The analytical epidemiological investigation suggests that there is a protective effect by washing hands before eating and using cutlery to minimise the risk of environmental contamination of hands or food.
16
Chapter 7 Environmental investigation
On Friday 2
nd June the Specialist Environmental Health Officer (Food) for Aberdeenshire Council
was informed of the first case. On Sunday 4th June the on call officer of the Aberdeenshire
Councils Environmental Health Service (EHS) was advised that there was another case associated with the New Deer campsite. The officer visited the New Deer Show ground and noted that it was heavily contaminated with sheep faeces. The officer collected samples at this time. 7.1 Environmental samples
On 4th June the following samples were collected
• There were several standpipes at the site but the water had been turned off and only one standpipe was working. A sample was obtained from this standpipe.
• The lying ground water was obtained from the only area of the site on which groundwater was evident.
• A sample was also obtained from a burn running at the boundary of the site.
• The sheep faeces samples were collected from four separate areas of the 20-acre site.
Further environmental sampling
• Samples of debris were obtained from footwear that had been used at the camp and sent for microbiological examination at GUHT.
• Samples of debris were also obtained from the climbing frame and sent for examination.
• Soil samples were taken from the New Deer site and submitted for examination. 7.2 Food and Water samples
The North of Scotland Water Authority reported no recent failures from the treatment works or reservoirs. No private water supply was available on site and there was no evidence that water had been drawn from streams. On the 5
th June the individual scout leaders
responsible for each troop at the camp were contacted to obtain the following information:
• What food was consumed during the two-day event.
• Where the food was purchased.
• How the food was prepared, stored and cooked.
• How drinking water was obtained and used.
Aberdeenshire EHS were advised that:
• Each troop purchased their own food from various sources.
• All food was prepared and cooked by the team leaders. The cooking methods varied from cooking on camping stoves to barbecues. There was no central catering point.
• All perishable food was stored in cool boxes or similar by each troop.
• Water was obtained from the nearest standpipe to each troops tent.
Samples of food from troops that had food left over were submitted to the GUHT laboratory for examination. The retail outlets where food was purchased were contacted. Samples were submitted from companies that produced meat products.
7.3 Sanitary Facilities
Purpose built toilet blocks with hand washing facilities were provided on site. These were found to be adequate. Leaders advised that they had reminded the Scouts to wash their hands.
17
Chapter 8 Microbiological investigations
8.1 Human microbiological results
All symptomatic individuals who had attended the scout camp were asked to provide a stool sample.
8.2 Individuals with Diarrhoea
The Cefixime Tellurite Sorbitol McConkey test was used on all human faecal specimens to isolate E. coli O157. All human samples were tested for campylobacter and 95% of samples were also tested for cryptosporidia, salmonella and shigella. 5% were not tested for cryptosporidia, salmonella and shigella because in the early stages of the outbreak it was not suspected that other bacteria or parasites were involved.
Table 9. Microbiological results of 48 specimens from primary cases with diarrhoeal symptoms.
Tested E. coli O157 Positive
Cryptosporidia positive
Campylobacter positive
E. coli O157 negative
Male 43 17 1 (dual infection)
1 26
Female 5 3 1 0 2
Total 48 20 2 1 28
48 faecal samples were tested of which 20 were positive for E. coli O157. Dual infection with cryptosporidia and E. coli O157 was isolated from 1 specimen. 1 further case of cryptosporidia and 1 case of campylobacter were isolated. All household contacts of positive cases of E. coli O157 were asked to submit a faecal sample as per local policy. One secondary case was confirmed.
8.3 Individuals with vomiting only
18 individuals had vomiting but no diarrhoea and the clinical description of the illness in these symptomatic individuals suggested an infection of viral origin. On 7
th June
individuals were asked to submit a faecal sample for virological testing. 7 samples were
tested and proved negative. 8.4 Veterinary microbiological results
Scottish Agricultural College (SAC) veterinary officers took random samples from the sheep that had been grazing on the New Deer Agricultural Show Ground prior to the camp.
Table 10. Microbiological results from animal specimens
Ewes Lambs
Positive- E. coli O157 11 3 Negative- E. coli O157 4 12 Positive- cryptosporidia 0 5 Total sampled 15 15
8.5 Food and water results
The drinking water was satisfactory. All food samples were negative for E. coli O157.
18
8.6 Environmental samples
The lying ground water was positive for E. coli O157. The sample from the burn was satisfactory. E. coli O157 was also isolated from soil samples. The grassed areas of the site were cut and the cuttings made into silage. A sample from the silage taken on the 11
th July was positive for E. coli O157.
8.7 Typing of isolates
E. coli O157 phage type 21/28 verotoxin 1 negative, verotoxin 2 positive was detected from all animal, human and environmental isolates by the Scottish E. coli O157 Reference Laboratory. Since the majority of Scottish E. coli O157 isolates share the same phage type (21/28), other typing techniques must be performed to distinguish potential outbreak samples from the background of unrelated sporadic cases occurring at the same time. Pulsed- field gel electrophoresis is a DNA fingerprinting technique that subdivides isolates within a particular phage type, thus characterising them more accurately. Using this technique all the New Deer camp isolates were found to be indistinguishable from each other. Furthermore the camp isolates have a different profile from the sporadic cases and are therefore not related.
19
Chapter 9 Communication
9.1 Parents of children attending the camp and all adult attendees.
On 4th June a letter from Grampian Health Board was sent to all parents advising them of
the current situation and giving advice on exclusion, sampling and infection control. On 7
th June a second letter was sent to the attendees and their parents to provide
updated information. This letter once again emphasised the importance of hand hygiene. The parents were also asked for their assistance with the investigation by filling in questionnaires. (Appendix 9 for copy of letters).
The parents telephoned the Communicable Disease Team for the results. On 5
th June a
dedicated results line commenced, staffed by the communicable disease nurses. Families and individuals with positive results were given advice on how to prevent secondary spread.
9.2 General Practitioners
On 4th June the out of hours Primary Care Co-operatives, G-DOCS and MorayDocs, and
Dr Grays Hospital in Elgin were advised of the potential outbreak by telephone. They were asked to advise anyone presenting with diarrhoea and who had attended the Millennium scout camp at New Deer to submit a stool sample and stay of school or work until 48 hours after symptoms had settled. On 5
th and 6
th June General Practitioners were
advised of the ongoing situation. (Appendix 10). 9.3 Education Department
On 6th June the Education Department was advised of the incident and the exclusion
policy. On 16th June a second letter advising on the amendments to the policy was sent
(Appendix 11).
Several Head Teachers contacted the CD Team by telephone for specific advice with regard to the routes of transmission of E. coli O157 and how to prevent of secondary spread.
The CD Team telephoned all Head Teachers of secondary schools where positive children were being allowed to attend. They were given, with parental consent, the children’s names and asked to ensure that sufficient soap and hand-drying facilities were available and that the children did not take part in any food preparation on school premises.
9.4 Press
A press conference was held after the OCT Meetings. Initially daily bulletins were issued however when public interest waned these were reduced accordingly (Appendix 12 for press statements).
9.5 Other Professionals
On 4th June the following were notified of the outbreak and updated regularly:
• Scottish Centre for Infection and Environmental Health (SCIEH)
• Scottish Executive
• Director of Public Health
• Chief Executive, Grampian Health Board.
20
Chapter 10 Conclusion and recommendations
The epidemiological findings in this outbreak support the results of the environmental and microbiological investigations. Camp organisers reported that sheep were grazing on the site the evening before the camp commenced. Consequently the grass was not cut as intended and the site was heavily contaminated with sheep faeces. The exceptionally heavy rainfall caused localised lying flooding leading to some areas becoming excessively muddy. The E. coli O157 isolated from the sheep faeces, sheep, wellington boots and the climbing frame were indistinguishable from the human isolates. All food and water samples were negative on microbiological investigation. All the twenty cases occurred within the incubation period indicating a point source origin. It is likely that due to the weather conditions and the camp activities that the children’s hands became contaminated. Although hand-washing facilities were available only 26% of the attendees always washed their hands before meals. Organisms could have been ingested by eating with soiled hands that served as the vehicle of transmission. This is supported by the finding that attendees from the district with the highest attack rate were least likely to wash their hands. Recommendations 1. Revised guidance on appropriate selection, preparation and management of sites should
be available to organisations proposing to hold any type of activity (e.g. camping, caravanning, agricultural shows, fairs etc) on land normally used for the grazing of animals.
2. Guidance on appropriate selection, preparation and management of sites should be
available to organisations proposing to hold any type of activity involving agricultural animals on public land not normally used for agricultural purposes e.g. agricultural shows on public land.
3. Further research is required to investigate the animal reservoir and carriage of E. coli
O157 and survival of the organism in the environment.
21
References 1. The Investigation and Control of Outbreaks of Foodborne Disease in Scotland, Scottish
Executive Health Department July 1999. 2. Report on the circumstances leading to the 1996 outbreak of infection with E. coli O157 in
Central Scotland, the implications for food safety and lessons to be learned. The Pennington Report 1997
3. Maule A. Environmental aspects of Escherichia Coli O157. International Food Hygiene
1999;9: 21-3. 4. Guidelines on bacteriological clearance: exclusion for pubic health reasons following
gastro-intestinal infection. Consultants in Public Health Medicine (Communicable Disease and Environmental Health) Working Group in Scotland.
22
APPENDIX 2 Membership of Outbreak Control Team
Dr Arun Mukerjee, Chairman & Consultant in Public Health Medicine (CD&EH) Grampian Health Board Fiona Browning, Communicable Disease Nurse, Grampian Health Board Dr John Cowden, Consultant Epidemiologist, Scottish Centre for Infection and Environmental Health, Glasgow Dr Jon Cresswell, Consultant in Public Health Medicine, Grampian Health Board Douglas Gray, Scottish Agricultural College, Bucksburn Colin Houston, Specialist Environmental Health Officer (Food), Aberdeenshire Council Dr Helen Howie, Senior Registrar in Public Health Medicine, Grampian Health Board Dr A Kindley, Consultant Paediatrician, Royal Aberdeen Sick Children’s Hospital Shaunagh Kirby, Public Relations Manager, Grampian Health Board John Littlejohn, Water Quality Manager, North of Scotland Water Authority Jayne Leith, Communicable Disease Nurse, Grampian Health Board Eleanor Lyall, The Scout Association David Milner, The Scout Association Dr T M S Reid, Consultant Microbiologist, Grampian University Hospitals Trust Secretariat: Mrs Diane McGregor, Grampian Health Board The Outbreak Control Team as convened on Sunday 4
th June 2000 and subsequently met on 7
th
June, 9th June, 12
th June and 21
st June 2000.
On 21
st June 2000 the Team was stood down.
