The Role of Contaminated Surfaces in the Transmission of Nosocomial Pathogens - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 44

During one outbreak of norovirus in a long-term care facility, five of ten environ-
mental samples collected after phenolic disinfection were positive, suggesting
widespread persistent contamination [ 47 ]. Positive sites included an elevator call
button used only by staff. The outbreak resolved following a second more thorough
facility-wide disinfection, suggesting that environmental contamination contrib-
uted to transmission. Various community outbreaks with norovirus have been
linked to shared computer keyboards [ 123 ], specific episodes of vomiting [ 124 ,
125 ] (for example, a kitchen assistant vomited into a sink that was used to prepare
vegetables) [ 124 ], contamination of carpets following a hospital outbreak [ 126 ] and
persistent widespread contamination in a UK hotel [ 127 ]. However, a key limitation
of these studies is that the role of symptomatic or asymptomatic staff carriage in
transmission often was not investigated.
Mathematical models that include the role of contaminated surfaces are rare,
but one study evaluated the likely economic impact of various control strategies for
norovirus including improved disinfection [ 128 ]. The model found that increased
disinfection alone or in combination with increased hand hygiene and using
protective apparel were the most effective strategies for the control and contain-
ment of norovirus outbreaks. However, prospective studies are required to quantify
the role of surface contamination in the spread of norovirus.
3.7.6 Revaluating “Negative” Studies
It is important to note that some studies report that environmental intervention is
ineffective in controlling various pathogens, indicated by the grey rows on
Table 3.4 . A critical re-evaluation of these studies suggests reasons why they did
not identify a significant reduction in transmission:
• Wilcox et al. [ 15 ]. There was virtually no impact on the frequency of C. difficile
environmental contamination on the wards when they switched from using a
QAC to bleach. Thus, it is not surprising that a significant reduction in CDI was
not consistently demonstrated in this cross-over study.
• Valiquette et al. [ 99 ]. A bundle of interventions were implemented over a period
of a few months, some of which were environmental. The bundle of interven-
tions was only given a few months to be effective.
• Dharan et al. [ 108 ]. The intervention was focused mainly on improving the
cleaning and disinfection of floors, which are not the high-touch, high-risk sites
that are likely to contribute most to transmission.
• Wilson et al. [ 107 ]. The cross-over study was performed in a declining preva-
lence of MRSA in the UK, so could have been underpowered to detect a clinical
impact.