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

Bloomfield et al December 2007 S39or their immediate environment, was necessary forinfection. 106Sources and spread of RT pathogens to the hands. Figure3 illustrates that the risk of exposure to RT pathogensvia hands depends on the extent to which thesepathogens are spread from an infected person duringnormal daily activities. Relevant data come from varioussources and are summarized below. Taken together,the data suggest that, when a household member isinfected, exposure of other household members viahands is likely to occur during normal daily activitiesand that the numbers of organisms involved are withinthose required to initiate infection if transferred to theeyes or nose.People infected with cold viruses shed large quantitiesof virus-laden mucus. Droplets of nasal secretionsgenerated by coughing, sneezing and talking can travelover a distance .3 m to contaminate surroundingsurfaces. 37,98,107-109 Up to 10 7 infectious influenza particlesper milliliter has been detected in nasal secretions.110 The mean duration of a cold is 7.5 days.Viral shedding may occur 24 to 48 hours before illnessonset but generally at lower titers than during thesymptomatic period. Titers generally peak during thefirst 24 to 72 hours of illness and decline within severaldays, with titers low or undetectable by day 5. Childrencan shed virus for up to 3 weeks, whereas immunocompromisedpeople may continue to shed virus forweeks to months. 98Infectious material can also be deposited directly onhands and tissues during sneezing and blowing thenose. Contamination of hands can occur by handshakingor touching contaminated surfaces. Pathogens shedinto the environment from these sources can survivefor significant periods and are readily spread aroundthe home to and from the hands and via handkerchiefsand tissues, tap and door handles, telephones, or otherhand contact surfaces:ddGwaltney and Hendley demonstrated that most subjectswith experimental colds had rhinovirus on theirhands and that virus could be recovered from 43% ofplastic tiles they touched. 104 For people with rhinoviruscolds, virus was found on 39% of hands and 6%of objects in their immediate environment. 100 Reeddemonstrated recovery of virus from naturally contaminatedobjects in the surroundings of personswith rhinovirus colds. 102In a recent study, Winther et al 111 recruited volunteerssuffering from colds to stay overnight in hotelrooms. After checkout, but before room cleaning,10 objects identified as frequently touched weresampled for rhinovirus. Virus was found on 35%of objects, including door handles, light switches,pens, faucet and toilet handles, and televisionremote controls. Some people contaminated noneor few sites, most contaminated several, and somecontaminated almost all (up to 8) sites. In a secondstudy in which the same subjects stayed overnightin a hotel room in which hand contact surfaces (lightswitch phone button and handset) had been contaminatedwith rhinovirus-contaminated mucus, 60% ofsubjects became contaminated with rhinovirus.d Ansari et al showed that hands readily pick up rhinovirusand PIV by touching contaminated objects. 112As much as 70% of infectious rhinovirus has beenshown to transfer to a recipient’s fingers after contactfor 10 seconds. 113 In a study with volunteers whohandled contaminated doorknobs or faucets, recoveryrates from 3 to 1800 plaque-forming units of rhinoviruswere obtained from fingertips. 114d In a study of US day care centers and domestichomes, influenza A virus was detected on 23% ofday care center surfaces sampled during the fall of2003 and 53% of surfaces sampled during the spring.Although no influenza was detected on home surfacesduring the summer, influenza was detected on59% of surfaces sampled during March in 5 homesin which there was an influenza-infected child. No viruswas recovered from 3 other homes in which allhousehold members were healthy. Influenza viruswas recovered most frequently from telephone receivers(80%) and least frequently from computerkeyboards (40%). Other surfaces found to be contaminatedincluded refrigerators; kitchen faucets; lightswitches; microwaves; TV remote controls; doorknobs;and bath, faucet, and toilet handles. Influenzavirus was recovered from 69% of the day care centerdiaper changing areas, indicating presence of virus ininfant feces. 94Transfer of RT infections via contaminated hands dependson the ability of the virus to survive and retainits infectivity outside the human host. The potentialfor survival varies significantly between nonenvelopedrhinovirus and RSV, compared with the enveloped influenzavirus and PIV:d Kramer et al 81 and Hendley et al 100 review data showingthat rhinovirus and RSV can survive for significantperiods (2 hours to 7 days for rhinovirus, up to6 hours for RSV) on dry surfaces and for at least 2hours on human skin.d Ansari et al 115 and Brady et al 116 showed that, althoughPIV can survive on nonabsorbent surfacesfor up to 10 hours, survival on hands was relativelypoor (1-2 hours).d Bean et al 117 showed that influenza virus could surviveup to 24 to 48 hours on nonporous surfaces and up to8 to 12 hours on cloth, paper, and tissues. By contrast,virus could be recovered from hands for only 5 minutesand then only if hands were contaminated with