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Detecting outbreaks ofE coli O157 infection in nurseries
  1. R J ROBERTS, Consultant in Communicable Disease Control
  1. Department of Public Health
  2. North Wales Health Authority, Hendy Road
  3. Mold, Flintshire CH7 1PZ, UK
  4. dr.richard.roberts{at}nwales-ha.wales.nhs.uk
  5. Head, PHLS Statistics Unit
  6. Public Health Laboratory Service
  7. 61 Colindale Avenue
  8. London NW9 5EQ, UK
    1. A V SWAN
    1. Department of Public Health
    2. North Wales Health Authority, Hendy Road
    3. Mold, Flintshire CH7 1PZ, UK
    4. dr.richard.roberts{at}nwales-ha.wales.nhs.uk
    5. Head, PHLS Statistics Unit
    6. Public Health Laboratory Service
    7. 61 Colindale Avenue
    8. London NW9 5EQ, UK
      1. R L SALMON, Consultant Epidemiologist

        Statistics from Altmetric.com

        Editor,—In their report of a serious outbreak ofE coli O157 in a nursery in North Wales, Al-Jader and colleagues recommend that more than one child with more than one bowel motion in a nursery should trigger action including “informing and seeking the advice of public health agencies”.1 Using data on healthy children reported in the paper we have calculated the additional work that would be generated for the Public Health Department in the district where the outbreak occurred if this policy was implemented.

        Of 19 well children on the ground floor of the nursery, six had more than one bowel motion on at least one of the half day sessions attended during the surveillance period.1 Well children attended on a median of six days during the period, giving an approximate total number of sessions attended of 228 (19×6×2). The probability of a well child having more than one bowel motion during any half day session was therefore about 0.026 (6/228). There are 385 day nurseries and playgroups in North Wales, with an average of 23 children per nursery.2 In an average size nursery the probability that two or more well children would have more than one bowel motion in a session on any one day is 0.12, equivalent to a false alarm every eight days.

        Therefore, if the suggested policy was implemented, and incidents were reported to the Public Health Department, this would result in approximately 46 inappropriate calls per day (0.12×385)—that is, 230 per week. Even if the normal background rate was ten times lower than that seen among well children during this outbreak, this would still result in just over three calls a week to the department reporting false alarms. The proposed “early warning system” is therefore almost unworkable, and the claim that it could have prevented 10–12 of the 31 cases in the outbreak needs to be reviewed.

        References

        Dr Salmon comments:

        Children who attend out of home child care are at increased risk for infectious diseases of which gastrointestinal tract infections are among the most common.1-1 Numbered among these are VT+E coli O157 infections which, as this outbreak showed, can cause severe disease. The challenge is to identify disease1-2 and prevent it.

        In this outbreak, given that the first two cases attended the nursery for two days after the onset of their disease on 21 August and the first case from the nursery was not reported until 1 September by which time 13 further symptomatic cases had occurred, our claim that 10–12 cases could have been prevented by taking further action, at this point, is straightforward. The toiletting record might have constituted a prompt to such action. We list a range of possible responses, particularly when the bowel motion is loose or offensive (inquiring about symptoms at home, suggesting a visit to the family doctor, arranging a faecal sample, and informing and seeking the advice of public health agencies). We were aware of the issue of specificity and did not suggest that all these activities should necessarily occur on every occasion that more than one child with more bowel motion was recorded. Most agree that faecal sampling needs, generally, to be encouraged.1-2 However, to combine the activities into a workable algorithm was beyond the scope of the report. Constructing an algorithm is worth attempting, however, since, as a starting point, a toiletting record constitutes a straightforward record used in a number of care settings.

        References

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