Norovirus gastroenteritis, although not a serious illness in itself, can have a severe impact in care settings
In this article…
- The clinical characteristics of norovirus gastroenteritis
- What you can do to prevent outbreaks of the illness
- How to manage outbreaks in hospital and community settings
- The impact of norovirus on healthcare
Gladys Xavier is deputy director of public health at Redbridge Primary Care Trust.
Xavier G (2011) How to prevent the spread of norovirus. Nursing Times; 107: 2, early online publication.
Norovirus gastroenteritis is an easily transmitted acute illness that commonly causes outbreaks in hospitals and community settings. It occurs particularly between November and April and often leads to ward closures in hospitals. While isolation of infected individuals can limit its spread, outbreaks cannot always be prevented. Stringent hygiene measures are vital to contain the virus.
Keywords: Norovirus, Gastroenteritis, Infection control
- This article has been double-blind peer reviewed.
5 key points
- Norovirus gastroenteritis outbreaks occur mainly between November and April.
- Outbreaks are particularly common in hospitals and semi-closed setting such as residential care settings, schools and workplaces.
- Outbreaks in hospitals commonly lead to ward closures.
- Isolation of infected individuals can limit the spread of outbreaks.
- Stringent hygiene measures are vital for infected individuals and anyone coming into contact with them.
Norovirus is the most common cause of infectious gastroenteritis in England and Wales with 10,676 cases reported from January to November 2010 (Health Protection Agency, 2011). The illness is generally mild and people usually recover fully within 2-3 days, leaving no long-term effects. Infection can occur at any age as immunity is not long-lasting (Kaplan et al, 1982); Box 1 lists its clinical characteristics.
Norovirus gastroenteritis is commonly referred to as winter vomiting disease due to its seasonality and typical symptoms. It is also known as small round-structured virus (SRSV) or Norwalk-like virus.
Outbreaks of norovirus gastroenteritis are common in semi-closed environments such as hospitals, care homes, schools and cruise ships. When an outbreak occurs in a hospital it is often necessary to close affected wards to help control the outbreak (Gastroenteritis Subcommitte, 1994). However, outbreaks are being increasingly recognised in the community and within hospitals and nursing homes in England. Although the illness is generally of short duration, outbreaks are common and often described as explosive (Chadwick et al, 2005).
Box 1. Clinical characteristics of norovirus
Incubation period: usually 24-48 hours.
Common clinical features: vomiting and/or diarrhoea accompanied by abdominal cramps. Some people also complain of head aches, fever, chills and muscle aches.
Onset of symptoms: typically 24-48 hours after ingestion of the virus, but can appear as early as 12 hours after exposure.
Reservoir: human gastrointestinal tract.
Transmission: person-to-person by the faecal-oral route; risk of infection from aerosols of projectile vomit. Environmental contamination, especially of toilets; food and drinks can become contaminated with norovirus through contact with an infected person.
Treatment: there is no specific treatment for norovirus; the illness should be allowed to run its course. People who are unwell should take plenty of drinks to replace lost fluids.
Other relevant features: infectivity lasts for 48 hours after resolution of symptoms. Because the virus is so small, it takes relatively few norovirus particles to cause illness (Institute of Food Science and Technology, 2008).
Norovirus outbreak management
An outbreak is defined as: “an epidemic limited to localised increase in the incidence of a disease, eg, in a hospital or closed institution”, or more simply as “two or more cases of illness linked to a common source” (Last 1995). An outbreak of norovirus should be suspected where one patient or resident shows signs of gastroenteritis (Dancer 2008).
Outbreak management has been defined as: ‘the process of anticipating, preventing, preparing for, detecting, responding and controlling outbreaks in order that health and economic impact is minimised’ (Gould 2009). Guidelines have been developed to standardise the approach of infection control teams, public health health teams, managers and healthcare professionals in hospitals and the community for both the investigation and control of institutional norovirus outbreaks . Specific guidelines for management of Norovirus outbreaks in hospitals are also available (Chadwick et al, 2005).
Within the general community, norovirus can cause sporadic cases and small clusters of gastroenteritis outbreaks with larger outbreaks occurring frequently, particularly during the winter months and often in residential homes, nursing homes, hotels and schools. In fact, the first recorded outbreak of norovirus gastroenteritis was reported in a primary school in Norwalk, Ohio over thirty years ago (Simmons et al, 2008).
Hospital management of outbreaks
Hospitals experiencing a norovirus outbreak follow outbreak management procedures in addition to standard infection control procedures when dealing with norovirus outbreaks; activities would include:
- Cohorting patients who are symptomatic;
- Reducing the number of staff and visitors entering the affected area to reduce the risk of the infection spreading;
- Excluding non-essential staff from affected areas;
- Cleaning and disinfecting vomit and faecal spillages promptly;
- Undertaking effective environmental disinfection (1,000ppm chlorine is currently recommended for hard surfaces, although other recently available disinfectants are also proving effective against norovirus);
- Implementing strict hand hygiene;
- Closing wards to new admissions to prevent the introduction of further susceptible individuals.
Community management of outbreaks
Outside hospitals, norovirus outbreaks can be devastating in closed or semi-closed communities, although gastroenteritis in the community may be associated with relatively mild and short-lived symptoms. The first port of call if an individual has symptoms consistent with norovirus should be to call NHS Direct or their GP for advice. When there is a strong degree of suspicion that the infectious agent is norovirus the following advice should be offered to the public and professionals:
- Patients wanting advice should contact NHS Direct or their GP by telephone.
- Advise patients against visiting their GP practice or hospital emergency department until symptom-free for 48 hours – norovirus infection is not a reason for admission to hospital in the absence of any other condition;
- Promote effective hand hygiene, including washing with soap and warm water for at least 15 secnds before and after contact with the patient, handling food or using the toilet;
- Ensure people with illness consistent with norovirus stay out of work or school until 48 hours after symptoms have resolved;
- Advice patients against visiting friends or relatives in hospitals or care homes until 48 hours after symptoms resolve, as there is a risk of infection being introduced into these establishments;
- Disinfect any surfaces of objects that could be contaminated with norovirus;
- Employ rigorous food hygiene where there is an infected person in the home;
- Prioritise outbreak investigations targeting care homes, schools and other establishments in the community;
- Inform local hospitals to raise awareness that norovirus is present in the community to ensure all patients admitted with diarrhoea and vomiting or who have had contact with anyone with diarrhoea and vomiting in the preceding 72 hours are isolated;
- Ensure prevention and control messages are circulated widely in the community.
Impact on healthcare services
The effect of norovirus on the provision of hospital and community services is striking. Outbreaks have a major impact not only in affected departments, but also throughout healthcare facilities and involve severe staff shortages, sometimes leading to hospital closures. There is considerable annual burden on healthcare (Lopman et al, 2003).
Prevention of outbreaks
Outbreaks of norovirus gastroenteritis are difficult to control in any setting because of the projectile nature of vomiting which causes extensive contamination of the surrounding surfaces and objects. Prevention largely relies on good assessment on admission and isolation of patients who are symptomatic with Norovirus. Prevention and control are particularly challenging where individuals are not socially competent (for example, very young children, the very elderly and confused). In residential homes and hospitals closure of affected areas to new admissions is thought to be important to reduce the length of outbreaks.
It has been suggested that closure is more likely to be effective if new admissions cease within four days of the commencement of the outbreak. Irrespective of the clinical setting, stringent hygiene is of paramount importance to reduce transmission (Barker et al, 2004).
Prevention of norovirus infections largely relies on good hygiene practices wherever people gather together such as at home, work, school and hotels. In this context, effective hygiene practice incorporates personal hygiene, safe food practices and environmental sanitation.
Members of the public need to be aware of risks from contaminated food, water and environmental contamination when somebody in the same household or a social contact has developed norovirus gastroenteritis. A degree of individual personal responsibility is required to break the chain of infection – infected individuals should isolate themselves as far possible and avoid preparing food for others.
People in potential contact with infected individuals also need to adopt a rigorous approach to hand hygiene at all times. Indeed, good handwashing practice is the single most important infection control measure. (Brooker and Nicol, 2003).
In nursing or residential homes, people with suspected norovirus infection should be managed with standard precautions, with careful attention to hand hygiene practices.
However, contact precautions should be used when caring for incontinent residents, during outbreaks in a facility, and when there is the possibility of splashes that might lead to clothing becoming contaminated. Disposable gloves and aprons should be worn for all contact involving affected patients and the surrounding environment. These should be discarded carefully to ensure hands do not become contaminated by contact with the outside of the gloves or apron as they are removed, and placed immediately into a clinical waste bag. Hands should then be washed (Chadwick, 2005).
Nurses who work in community settings will frequently encounter patients suffering from infectious gastroenteritis likely to be caused by norovirus. They play an important role advising patients and their families how to contain the spread of infection and explaining how to reduce the severity of symptoms.
Laboratory testing is not necessarily indicated to verify the existence of an outbreak once an illness like norovirus is widespread within the community. Public health efforts would probably be better spent educating the public to avoid illness by taking personal health action (Graham et al, 1994).
Current level of norovirus activity
In weeks 45–48 of 2010 the Health Protection Agency (HPA, 2010) recorded 41 outbreaks of norovirus in hospitals, 37 of which led to ward closure. This is almost 50% more than the number recorded the previous month. Although people can suffer from norovirus at any time of the year, activity increases in the winter months with the majority of cases occurring between October and April.
Data from the number of calls to NHS Direct related to vomiting exceeded the threshold level (4.8% of calls for two consecutive weeks) consistently for the four weeks before publication. This indicates that levels of norovirus are increasing across the UK (HPA 2009).
Its mode of spread means is not always possible to avoid becoming infected with norovirus. However, good hygiene and isolation of infected individuals as far as possible can help to limit the spread of the infection.
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