How to prevent the spread of norovirus
Norovirus has a significant impact on healthcare resources. Nurses can help to prevent its spread by maintaining good hand hygiene and infection control measures
In this article…
- The impact of norovirus on healthcare resources
- Key symptoms and how the virus is transmitted
- How to prevent the spread of norovirus
Terry McGeary, formerly bioscience lecturer at Clydebank College, now freelance science writer and photographer who lives in East Kilbride.
McGeary T (2012) How to prevent the spread of norovirus. Nursing Times; 108: 6, 20-22.
Norovirus has gained notoriety as the winter vomiting bug. While the infection is usually self-limiting, its impact on healthcare resources is significant. This article advises nurses how to maximise infection control strategies during an outbreak.
Keywords: Norovirus/Outbreak/Hand hygiene/Infection control
- This article has been double-blind peer reviewed
- Figures and tables can be seen in the attached print-friendly PDF file of the complete article
5 key points
- Norovirus is one of the major organisms responsible for viral gastroenteritis
- While debilitating, infections are usually self-limiting and generally not harmful in the long term
- Symptoms include vomiting, non-bloody diarrhoea, abdominal cramps and nausea
- Young children and older people are at risk of dehydration; the virus has been linked to cause of death in older people
- Good hand hygiene is vital to prevent the virus spreading
Norovirus - originally known as Norwalk virus - is one of the major organisms responsible for viral gastroenteritis.
Taxonomically, it is a calicivirus; it is a single-stranded, non-enveloped (naked) RNA virus.
The original strain was identified from an outbreak in a school in Norwalk, Ohio in 1969, and the names Norwalk-like viruses and noroviruses are also used for various related genogroups and variant strains identified since.
According to Narayan and Albrecht (undated), Norwalk-like viruses (small round structured viruses or SRSVs)
are among a number of gastroenteritis-associated viruses such as astrovirus and rotavirus.
The virus has gained notoriety from newspaper headlines about outbreaks of “winter vomiting bug” on cruise liners
and in the community. While infections are temporarily debilitating, they are self-limiting and generally appear not to be harmful in the long term. However, the high rate of cross-infection and the resulting inconvenience and financial implications have drawn attention to the virus.
The following examples illustrate the impact of the virus. The Health Protection Agency (2009) estimated losses of £115m in three NHS hospital trusts in Avon in 2002-03, due to staff absence and ward closures attributable to gastrointestinal disease, mainly norovirus infection.
From 2009 for England and Wales and 2010 for Scotland, secure web-based dedicated systems were set up for voluntary reporting of norovirus outbreaks and resulting ward closures.
The HPA (2009) reported 262 outbreaks in 43 trusts from January to March 2009. These accounted for 2,814 patients and 747 staff being affected, with 82% of outbreaks resulting in ward closures and 4,000 bed-days being lost. Clearly, the impact of norovirus can be immense.
More recently, the HPA (2010) found that within 175 samples from patients taken during outbreaks between December 2009 and January 2010, seven norovirus genotypes were detected. The outbreaks were in the following three main areas:
- Hospitals and nursing homes;
- Schools, nurseries and childcare centres;
- Restaurant and food-borne sources.
Most cases (85%) were due to GII-4 noroviruses, with variant strain 4 (GII-4v4) being the most frequently detected variant strain (HPA, 2010).
Symptoms listed by the Centers for Disease Control and Prevention (2011) include vomiting, non-bloody diarrhoea with abdominal cramps and nausea. These appear following an incubation period of 24-48 hours, although there are instances where symptoms present after only 12 hours following exposure to the virus.
Blacklow (1996) found adult volunteers inoculated with the virus developed a transient mucosal lesion of the proximal small intestine but had no colon involvement; this suggests norovirus infection spares the large intestine, hence faecal leucocytes are not present in stool samples. This feature has been used to help differentiate the infection from others such as salmonellosis, shigellosis or C difficile infection.
However, findings by Yu et al (2007) contradicted the common notion that faecal leucocytes are not present in norovirus patient stools. An outbreak in 2005 among students at Worcester Polytechnic Institute in Massachusetts resulted in 39 students being admitted to three local hospitals. Of seven students tested for faecal leucocytes, all proved positive.
Norovirus symptoms, although severe and distressing, may last between one and three days after which recovery is usually complete.
While anyone can become infected, young children and older people are at a higher risk of dehydration than others from failure to retain fluids.
A study of children hospitalised with either rotavirus or norovirus concluded that norovirus was a major cause of gastroenteritis in children and could cause non-febrile convulsions, particularly in young infants (Chen et al, 2009). Long-term neurological consequences were uncommon when cases were followed up one year later.
Similarly in adults, although in most cases there appear to be no long-term effects, norovirus may occasionally pose some risk.
Harris et al (2008) studied the relationship between norovirus infection and cause of death in older people aged 65 or over. They estimated that an average of 80 deaths per year in England and Wales might be associated with norovirus gastroenteritis, after analysing death registration data from the Office for National Statistics together with laboratory results from the HPA for 2001-06.
How contagious is norovirus?
The faecal-oral route is recognised as the main mode of transmission. The CDC (2011) states: “Norovirus is transmitted by hands contaminated through the faecal-oral route, directly from person to person, through contaminated food or water, or by contact with contaminated surfaces or fomites. Aerosolised vomitus has also been implicated as a transmission mode.”
The well-known contagious nature of the infection appears to be attributable to three notable disease features:
- A minute inoculum can start an infection - as few as 10 viral particles can cause infection (Centers for Disease Control and Prevention, 2007);
- Infected people are themselves infectious before developing symptoms, for example an American football team unknowingly infected by a food source eaten before a game passed the virus on to the opposing team, only later suffering vomiting and diarrhoea (Becker et al, 2000);
- The virus does not decrease in contagiousness or pathogenicity during outbreaks (Teunis et al, 2008).
In addition, Teunis et al (2008) found that the infectivity of the prototype Norwalk virus does not alter by passage through an infected host. Outbreaks therefore occur easily and secondary infections have an equally devastating, if temporary, effect.
There is no specific treatment for norovirus infection and no vaccines available. Short-term immunity is known to build up but, as the virus appears in different strains, existing antibodies will give no protection against later outbreaks.
Due to norovirus’s high infectivity and persistence in the environment, its transmission is difficult to control through routine sanitary measures. Stringent hygiene practice is therefore key to containing this disease.
For example, monitoring cleaning of ships’ toilet areas revealed that cleaning to a level higher than what would normally be acceptable significantly reduced the likelihood of norovirus outbreaks on board (Carling et al, 2009).
In healthcare, stringent measures must be taken to avoid cross-infection between patients, as well as between patients and staff or other possible contacts in hospital. A proactive approach to hygiene seems appropriate since transmission is possible before symptoms appear.
The Health Protection Agency (2011) has published guidelines on the management of outbreaks in health and social care settings.
During an outbreak of norovirus, the HPA (2011) recommends using liquid soap and warm water as part of the World Health Organization 5 Moments of Hand Hygiene for hand decontamination. Patients and visitors should also be urged, and assisted if necessary, to wash and dry hands and understand why this is important.
Handwashing with soap and water is one of the most important processes in controlling cross-contamination and avoiding infection.
As part of the Germs: Wash Your Hands of Them campaign, Health Protection Scotland provided infection control resources including poster material on the 5 Moments for Hand Hygiene, guidance for effective hand sanitising and policies for infection control (tinyurl.com/HPS-resources). HPS (2009) reported an increase in compliance with hand hygiene from 68% to 93% as a result of this campaign.
The NHS in England ran the Cleanyourhands campaign to encourage hand hygiene. The WHO has a SAVE LIVES: Clean Your Hands global annual campaign.
During an outbreak of norovirus, the HPA (2011) recommends cleaning and removal of organic soiling with detergent before disinfection to maximise the effectiveness of surface disinfectants. It suggests disinfection is carried out using 0.1% sodium hypochlorite (1,000ppm available chlorine) following manufacturers’ guidelines.
Staff should wear personal protective equipment (PPE) when working with corrosive or caustic materials; such materials should not be prepared or used in poorly ventilated areas (HPA, 2011). Sodium hypochlorite may degrade environmental surfaces with repeated use (HPA, 2011).
Recommendations for environmental decontamination during an outbreak include:
- Increase the frequency of cleaning by dedicated staff;
- Clean from least likely contaminated areas to most highly contaminated areas;
- Use disposable cleaning materials or dedicated reusable cleaning materials for use in the affected area;
- Disinfect with 0.1% sodium hypochlorite after cleaning;
- Pay attention to frequently touched surfaces such as bed tables and door handles;
- Cleaning and other staff should follow standard infection control procedures and wear personal protective clothing including gloves and aprons.
Outbreak control measures recommended by the HPA are listed in Box 1.
BOX 1. SUMMARY OF OUTBREAK CONTROL MEASURES
- Close affected bays to admissions/transfers
- Keep room/bay doors closed
- Put up signs to inform visitors and staff
- Ensure staff are aware of norovirus and how it is transmitted
- Ensure staff know about work exclusion policies and to go off duty as soon as they experience any symptoms
- If possible, allocate staff to either affected or non-affected areas
- Provide information on the outbreak and control measures
- Inform visitors of risks and how to reduce them
- Use liquid soap and warm water as per WHO 5 Moments for Hand Hygiene
- Encourage and assist patients with hand hygiene
- Remove exposed food (fruit bowls)
- Prevent staff eating in clinical area
- Undertake intense cleaning of affected areas and toilets
- Decontaminate frequently touched surfaces with detergent and disinfectant (1,000ppm available chlorine)
- Record patient and staff symptoms
- Monitor patients for signs of dehydration and treat
- Audit personal protective equipment
- Use gloves and aprons
- Wear masks if there is a risk of droplets or aerosol
- Use single patient- use where possible
- Decontaminate equipment immediately after use
- Use water-soluble bags placed in a secondary bag when discarding linen from a closed area
- Wear personal protective equipment
- Remove spillages with paper towels
- Decontaminate area with disinfectant containing 1,000ppm chlorine.
- Discard waste as clinical waste
- Remove PPE and wash hands with liquid soap and water.
Source: HPA (2011)
Norovirus is a highly infectious virus and causes a severely unpleasant gastroenteritis. In healthcare, outbreaks have organisational and financial implications. Strict hygiene routines and an appropriate response are essential to avoid outbreaks, contain them or minimise their consequences.
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Becker K et al (2000) Transmission of Norwalk virus during a football game. New England Journal of Medicine; 343: 17, 1223-1227.
Blacklow N (1996) Norwalk virus and other caliciviruses. In: Baron S (ed) Medical Microbiology. Galveston, Texas, TX: University of Texas Medical Branch.
Carling P et al (2009) Cruise ship environmental hygiene and the risk of norovirus infection outbreaks: an objective assessment of 56 vessels over 3 years. Clinical Infectious Diseases; 49: 9, 1312-1317.
Centers for Disease Control and Prevention (2011) Norovirus: Technical Fact Sheet.
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Chen SY et al (2009) Norovirus infection as a cause of diarrhea-associated benign infantile seizures. Clinical Infectious Diseases; 48: 849-855.
Harris P et al (2008) Deaths from norovirus among the elderly, England and Wales. Emerging Infectious Diseases; 14: 10, 1546-1552.
Health Protection Agency (2011) Guidelines for the Management of Norovirus Outbreaks in Acute and Community Health and Social Care Settings.
Health Protection Agency (2010) Regional and National Network for the Detection and Characterisation of Noroviruses; December 2009-January 2010. London: HPA.
Health Protection Agency (2009) Healthcare-Associated Infections in England. London: HPA.
Health Protection Scotland (2009) National Hand Hygiene NHS Campaign. Compliance with Hand Hygiene - Audit Report Health Protection Scotland. July 2009, Glasgow.
Narayan N, Albrecht H (undated) Viral agents of gastroenteritis. In: Microbiology and Immunology On-line. University of South Carolina School of Medicine.
Teunis P et al (2008) Norwalk virus: How infectious is it? Journal of Medical Virology; 80: 1468-1476.
Yu C et al (2007) Clinical and laboratory findings in individuals with acute norovirus disease. Archives of Internal Medicine; 167: 17, 1903-1905.
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