Using “health outcomes” as the basis for developing effective and sustainable hygiene interventions – is 2019 the time for a rethink?

This is a guest post by Prof Sally Bloomfield…

For many years, “5 log reduction” (LR) has been the gold standard for disinfectant efficacy despite absence of dose:response data linking it to clinical outcomes.  The family of EN tests now used to support claims for disinfectant products has its origins in the European Suspension Test (5LR, 5 mins, 5 test organisms) where 5 LR was probably chosen because it is the limit of sensitivity in an assay where, traditionally, the initial bioburden is 108 colony forming units.  For soap, detergent or dry wiping procedures, until recently their effectiveness has been assumed – possibly on the basis that they produce visible cleanliness? It is only recently that we have had access to efficacy data based on lab models.  A trial of EN 1699 handwashing test showed a mean 2.76 LR when hands contaminated with E .coli are washed with soap.

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A domestic outbreak of gastroenteritis

domesticEarlier this year, I wrote about an outbreak of norovirus in a US car dealership. There, the outbreak was traced to a toddler “spraying” norovirus around a public restroom and baby-changing station. Regrettably, I now have my own experience to relate.

Last Wednesday (let’s call it outbreak day 1), our 18-month old toddler “sprayed” projective vomit around our porch. My wife cleaned up the mess (not with dry paper towels, as in the US car dealership outbreak but with detergent and water). On outbreak day 3, 36 hours later, my wife presented (grumpily) with acute gastroenteritis. We made every effort to limit domestic horizontal transmission (including regular bleach disinfection of contact surfaces in the bathroom and cohorting of personal effects) but to no avail; a little over 24 hours later on outbreak day 4, I endured acute gastroenteritis.

What do we learn from this?

  • Transmission routes for viral gastroenteritis are very difficult to disentangle. It seems likely that my wife acquired norovirus whilst cleaning up the vomit, and I acquired norovirus from my wife somehow. Of course, this may not have been the case. My wife could have acquired the infective agent in a number of ways from our toddler. Also, I could have acquired it directly from our toddler and not my wife. Finally, a common source seems unlikely due to the ‘domino’ type progression, but cannot be discounted. If I can’t be sure of transmission routes amongst three people in a single household, how can we hope to understand transmission routes on a hospital ward or aboard a cruise ship
  • We are not sure what caused the outbreak. None of us were in the mood to submit a specimen during the outbreak and, even if we had bothered to collect one, how would we have got it analysed? Take it to the GP (bad idea) or hospital lab (even worse) or post it (unhappy mail carrier). Thus, our understanding of the prevalence and aetiology of gastroenteritis in the community is woefully lacking.
  • It’s been expensive. I was unable to travel to mainland Europe for an important meeting last week due to this outbreak, which has meant re-booking the trip at expensive short notice. Plus, I am still unable to go to work today (since I’m still within 48 hours of my symptoms). Whilst I am fortunate in that my work can be conducted from home, others are not so lucky. I suspect that the economic impact of viral gastroenteritis is hugely underestimated. In fact, I am not sure anybody has really tried to estimate it, let alone underestimate it, due to the lack of meaningful prevalence data.
  • Horizontal transmission is difficult to block. We took every precaution that we could think of to prevent horizontal transmission, without success. Part of the problem was that we did not recognise the outbreak immediately. This principle translates to preventing horizontal transmission in hospitals: the pre-diagnosis management of patients with diarrhoea and vomiting is crucial.
  • It’s very, very unpleasant. We are a young, (fairly) healthy family and each of us were laid out for 12 hours, and pretty useless for at least 24 hours. I can see how somebody who is already unwell and in hospital would be affected very badly indeed. I recommend that anybody who cares for patients in hospitals with acute gastroenteritis should be sure to try it themselves, in the interests of empathy.

Could we have done a better job of preventing the spread of this acute bout of gastroenteritis through the Otter household? Probably, through better outbreak identification and more stringent cohorting (perhaps with universal gowns and gloves, and liberal use of masks). But really, I’m just counting our blessings that we didn’t all get it at the same time.