Effects of cleaning and disinfection in reducing the spread of Norovirus contamination via environmental surfaces
Introduction
Noroviruses (NVs) are a major cause of gastroenteritis, which spreads rapidly in premises such as hospitals, hotels, day-care centres, residential and domestic homes.1., 2., 3., 4., 5. NV hospital outbreaks are common, and frequently result in ward closures because of the need to prevent further spread and to facilitate environmental cleaning. The scale of the problem in the community was highlighted by a recent study of rates of infectious intestinal disease in the UK. Wheeler et al.6 estimated that for every one case of NV reported to national surveillance, a further 1562 cases occur in the community. Based on the number of reported cases, Evans et al.7 estimated the total number of cases in the community to be around 3 million per year.
The likelihood of airborne transmission of NV was demonstrated in an outbreak at a restaurant where no food source was implicated, but an analysis of the attack rate showed an inverse correlation with the distance from a person who had vomited.3 Microbiological data show that projectile vomiting associated with NV infection may distribute up to 3×107 virus particles as an aerosol,8 whilst environmental sampling during outbreaks of vomiting and diarrhoea confirm that widespread dissemination of NV occurs on hand contact and other surfaces.2., 9. From such data and from estimates which suggest that the infective dose for NV may be as low as 10–100 particles, Caul8 concluded that, in addition to possible aerosol inhalation, hands and surfaces also play an important part in facilitating transfer of NV infection, either by direct faecal–oral transfer or by transfer to foods that are eaten without further cooking.
The potential for transmission of NV via environmental surfaces is also supported by epidemiological studies, the most compelling evidence coming from recurrent outbreaks of NV infection in successive cohorts of guests in hotels and on cruise ships.9., 10., 11., 12. From the patterns of infection, it is concluded that whereas aerosols are probably the main route of dissemination within a cohort of guests, contaminated fomites are the most likely factor responsible for sustaining a succession of outbreaks. Other data comes from an investigation of an NV outbreak at a wedding reception, which showed that the likely route of transmission was from a kitchen assistant who had vomited in a sink that was subsequently used for preparing vegetables eaten by the wedding guests.13 Analysis of risk exposure during an outbreak of NV gastroenteritis in an elderly care unit showed that areas where patients had vomited were the most significant factor for the spread of NV to staff.1 Further evidence of environmental transfer comes from a report of two carpet fitters who became ill after removing a carpet from a hospital ward 13 days after the last case in an NV outbreak.14 The role of contaminated soft furnishings in transmission and the difficulties these pose for decontamination is highlighted by the outbreak that occurred among school children who attended a theatre in which a vomiting incident had occurred on a previous day.15 Guidelines have been issued for the control of NV outbreaks in hospitals that stress the importance of preventing staff and patient movements to other areas, thorough handwashing and effective environmental decontamination.16
Since NV is uncultivable in the laboratory, little is known about the length of time it remains infectious in the environment or the effectiveness of disinfection procedures used to inactivate the virus. The development of a broadly reactive reverse transcriptase polymerase chain reaction (RT-PCR) has facilitated the detection of the virus in both clinical and environmental samples.17 In this investigation, we have used an RT-PCR assay to study the transfer of NV from contaminated faecal material via fingers and surfaces, and compared the effectiveness of detergent-based cleaning alone with hypochlorite disinfection for eliminating NV from faecally contaminated surfaces.
Section snippets
NV-contaminated faecal sample
A homogenized clinical faecal sample (obtained from Bristol Public Health Laboratory) that was positive for NV genogroup II when assayed by RT-PCR was used throughout. The number of virus particles per gram of sample was not known, but it was found that positive amplicons could be obtained by RT-PCR up to a dilution of 1:2000 of the sample (data not shown). A faecal sample negative for NV when assayed by RT-PCR was used as a negative control.
Transfer of NV via fingers and surfaces
To contaminate fingers, 150 μL of the faecal sample,
Contamination of fingers and transfer of NV to surfaces
In a series of four replicate experiments, faecally contaminated fingertips were used sequentially to touch a series of eight clean melamine surfaces, without recontaminating the fingers for each new surface touched (Figure 1). For the first four surfaces in the series, all four replicates were positive for NV. For surfaces five and six, three out of four replicates were positive, for surface seven, one out of four was positive, and for surface eight, all four replicates were negative. In a
Discussion
This investigation established a model to study transmission of NV from an infectious source via fingers, cloths and contact surfaces. RT-PCR was used to confirm transfer of NV from surface to surface. In the absence of a tissue-culture method for NV, the correlation between viral RNA detection and numbers of virus particles and/or their infectivity is impossible to determine. Thus, although it can be argued that the absence of detectable RNA is likely to indicate the absence of infectious
Acknowledgements
The authors thank Dr Martin Jones and Debbie Stevens for helpful discussions and Unilever Research for funding this study.
References (30)
- et al.
Transmission of a small round structured virus by vomiting during a hospital outbreak of gastroenteritis
J Hosp Infect
(1994) - et al.
The role of environmental contamination with small round structured viruses in a hospital outbreak investigated by reverse-transcriptase polymerase chain reaction assay
J Hosp Infect
(1998) The role of viruses in gastrointestinal disease in the home
J Infect
(2001)The role of viruses in gastrointestinal disease in the home
J Infect
(2001)Small round structured viruses—airborne transmission and hospital control
Lancet
(1994)- et al.
Viral gastroenteritis aboard a cruise ship
Lancet
(1989) - et al.
Management of hospital outbreaks of gastro-enteritis due to small round structured viruses
J Hosp Infect
(2000) - et al.
Concentration and detection of caliciviruses from food contact surfaces
J Food Protect
(2002) - et al.
Transmission of viruses via contact in a household setting: experiments using bacteriophage φX174 as a model virus
J Hosp Infect
(2000) - et al.
Hygiene in the home: relating bugs and behaviour
Soc Sci Med
(2003)
Inactivation of a feline caliciviris, a Norwalk virus surrogate
J Hosp Infect
Evidence for airborne transmission of Norwalk-like virus (NLV) in a hotel restaurant
Epidemiol Infect
Study of infectious intestinal disease in England: rates in the community, presenting to general practice and reported to national surveillance
BMJ
General outbreaks of infectious intestinal disease in England and Wales: 1995 and 1996
Commun Dis Public Health
Widespread environmental contamination with Norwalk like viruses (NV) detected in a prolonged hotel outbreak of gastroenteritis
Epidemiol Infect
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