Abstract
The norovirus season is upon us and it is therefore timely to consider control strategies in healthcare settings. In this issue of JIP, Curran et al. (2016) provide some novel insights into factors that might contribute to outbreak prevention, preparedness and management in both acute and long-term care environments.
Norovirus is a leading cause of acute gastroenteritis (diarrhoea and vomiting) and is associated with 18% of cases of the disease globally, across high-, medium- and low-income settings. Although often a mild, self-limiting disease, severe outcomes are common among children and the elderly (Lopman, 2015). There are 32 different genotypes of norovirus, but the G11.4 genotype is the predominant cause of outbreaks associated with healthcare and is also responsible for most cases in children worldwide (Lopman, 2015). Immunity to norovirus is both genotype specific and of limited duration, and the cycling of new G11.4 variants every 2–4 years enables the virus to evade the immune system. In addition, susceptibility to the virus is not universal with as many as 50% of individuals exposed to the virus not developing the illness (Patel et al., 2009).
One of the major challenges to understanding the epidemiology of norovirus has been the lack of a mechanism to culture the virus, as until very recently a robust cell culture system was not available. The development of PCR techniques has improved our ability to detect norovirus in clinical and environmental samples, however the test identifies viral RNA and cannot distinguish viable viral particles and may also detect norovirus RNA in the stool of healthy people. Transmission of norovirus in care settings occurs primarily through person-to-person spread via a faecal–oral route, in the community, exposure to contaminated food leads to significant point source outbreaks (Lopman et al., 2011). Contact with vomit either directly, by aerosolisation, or via contaminated surfaces may be a contributory factor in outbreaks in healthcare and other confined settings such as residential homes and cruise ships (Patel et al., 2009). Outbreaks in healthcare and long-term care settings are common and associated with considerable morbidity, mortality and costs. The Hospital Norovirus Outbreak Reporting System in England alone received reports of 858 outbreaks in the 2014/15 season (Public Health England, 2015).
The early detection and effective management of cases to prevent person-to-person transmission is essential to reduce this burden, however, the study reported by Curran et al. (2016) in this issue of JIP entitled ‘Where Is Norovirus Control Lost (WINCL)?’ illustrates that unrecognised transmission events occur frequently in both acute and non-acute care settings. The study identified that in 50% of outbreaks included in the study, the person identified as the index case had actually been present in the care setting for longer than the incubation period for norovirus, suggesting that a previous case or contamination episodes are being missed. The study provided some insights into why cases of norovirus are likely to be missed, in particular, the attribution of gastrointestinal symptoms to other causes such as antibiotics, laxative use or co-morbidities. The readiness to attribute these symptoms to factors other than gastrointestinal infection might be influenced by what has to happen if infection is considered likely, i.e. patient placement in a single room. There are often difficulties finding a bed – without the additional specific requirement for a single room. Additionally, assessment error might be influenced by the drive to accurately identify clinical cases of Clostridium difficile. The guidance on the diagnosis of Clostridium difficile recommends considering other factors that might explain the symptoms before making a diagnosis of Clostridium difficile infection (CDI), i.e. consider non-infectious before infectious causes. Implementation of this process may adversely affect the capacity of clinical staff to consider infections such as norovirus as the cause of the symptoms displayed by the patient (Department of Health, 2012). The WINCL study shows that erring on the side of caution during norovirus season, i.e. consider likely to be norovirus until proven otherwise, may increase case detection and decrease transmission opportunities.
The other factor highlighted by Curran et al. (2016) is the evidence for unrecognised transmission of norovirus suggests that either standard control of infection precautions (SCIP) are ineffective in preventing transmission or they are being ineffectively practiced. As Curran herself points out in another paper, there is much confusing and conflicting advice with regard to the meaning and application of SCIP which may contribute to poor compliance (Curran, 2015). Even where protective clothing is used with the intention of preventing transmission, there is increasing evidence that the use of gloves has an adverse effect on hand hygiene and may increase the risk of cross-contamination because they are put on too early and removed too late (Loveday et al., 2013) .
The lessons of the WINCL study remind us that norovirus is the most common cause of outbreaks in healthcare settings and that both infection control practitioners (ICPs) and clinical professionals must be vigilant to ensure proactive detection and control measures are in place. In particular, ICPs should consider how they sustain a heightened awareness of norovirus in the context of managing the diagnosis of CDI; the messages are complex and readily lost especially in fast-moving, care settings where staff are under pressure.
The last lesson from the WINCL study is this: this multi-centre study, which many readers of this editorial might have taken part in, shows the synergistic power of researchers working together to gain insights into that which we do not yet know.