The effectiveness of hand hygiene procedures in reducing the risks ...

S50 Vol. 35 No. 10 Supplement 1 Bloomfield et alTable 16. In vitro tests to determine the efficacy ofalcohol hand gel containing 62% ethanol: contact time30 secondsVirusLog reductionAdenovirus 5 0.33Adenovirus 6 0.33Adenovirus 7 0.27Adenovirus 8 0.66Coronavirus 229E 2.83Coronavirus OC43 2.00Echovirus 9 5.00Echovirus 11 4.83Influenza A2 6.0Influenza B 6.0Parainfluenza 1 (sendai) 6.0Parainfluenza 4b 3.0Respiratory syncytial virus 3.17Rhinovirus 18 3.83Rhinovirus 2 5.0Rhinovirus 14 6.0ethanol and 2-propanol were more effective than soapin reducing bacterial counts on hands. 203 Using theASTM 1174 method, Sickbert-Bennet et al 169 showedthat applying protein to hands did not produce any significantreduction in efficacy of ABHS or handwashingbut produced a modest but significant increase; log reductionsfor handwashing were 1.18 to 1.39 and 1.56to 1.87 in the absence and presence of protein, respectively.Log reductions for ABHS were 0.18 to 1.07 and1.35 to 1.55 in the absence and presence of protein,respectively.Assessing the efficacy of handwashing andABHS by Quantitative Microbiologic RiskAssessmentOne of the problems in developing hygiene promotionpolicies is the lack of quantitative data on the relativehealth impact of different hygiene interventions.Although intervention studies yield quantitative dataon health impact, as discussed in section 4.2, the reliabilityof these estimates is difficult to confirm. By contrast,in vivo and in vitro tests are more economic toperform and can be used to determine relative efficacyof different procedures but give no assessment of howthe contamination reduction on hands correlates withhealth impact. In an attempt to overcome these problems,Haas et al have applied the technique of QuantitativeMicrobial Risk Assessment (QMRA) to estimatethe relative health benefits resulting from use of differenthygiene procedures. 204 This approach involves usingmicrobiologic data from the published literaturerelated to each stage of the infection transmission cycleto calculate infection risk.In a recent study, 205 these investigators developeda model for studying the effect of hand contact withground beef during food preparation, which was usedto study the impact of handwashing and use of ABHSin preventing subsequent transference from the handsto the mouth compared with no handwashing. PathogenicE coli and E coli O157:H7 were selected for thisstudy because it is known from other investigations 206that handling ground beef during home food preparationposes a risk of infection with E coli. To performthe risk assessment, data on the density of pathogensin ground beef, transference from beef to hands, removalby handwashing or ABHS, rate of transfer fromhand to mouth, and infectivity of ingested pathogenswere obtained from the literature and, after screeningfor data quality, were used to develop probability distributions.For assessing log reductions produced by handhygiene procedures, only in vivo panel testing datawere considered. The median log reduction used inthese calculations was 0.3 (range, 0.2-3.0) for handwashingand 4.3 (range, 2.6-5.8) for ABHS.Table 17 shows the estimates of the infection riskfrom handling raw beef, as obtained from the analysis.The authors note that these risks are conditional inthe sense that they quantify the risk to an individualwho has handled ground beef and who engages inhand-to-mouth activity. The probability that an individualwill engage in such behavior is not known, and,therefore, a direct comparison with actual disease ratescannot be made. However, with some plausible assumptions,it was assessed that, assuming that there are 100million individuals in the United States, each of whomhandles ground beef once per month, this results in1.2 3 10 9 contacts per year. Assuming that 10% of theseindividuals contact hand to mouth after handlingground beef, this amounts to 1.2 3 10 8 incidents peryear. For E coli O157:H7, using the median risk, thiswould result in an estimate ranging from 0.014 infectionsper year if all individuals washed their handswith soap following contact with ground beef to 0.7 infectionsper year if no handwashing is done. This wouldequate to a 98% median risk reduction for handwashingcompared with no handwashing. If an ABHS was used,this would result in an estimate of 0.00005 infectionsper year if all individuals used ABHS following contactwith ground beef. This would equate to a 99.9996%median risk reduction for use of ABHS compared withhandwashing.This study follows an earlier study by Haas et al 207 tocalculate risks associated with hand-to-mouth transferafter diaper changing of a baby infected with Shigella.Based on this model, it was calculated that the probabilityof acquiring infection was between 24 of 100 and 91of 100 for those who used handwashing with soap afterchanging diapers. This was based on panel test data