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Outbreaks of norovirus can have a significant operational and financial impact on healthcare establishments.
Aim
To assess whether containment of symptomatic patients in single rooms and bays at the beginning and end of norovirus outbreaks reduced the length of bed closure.
Methods
In 2007, we introduced a new strategy to limit the operational impact of hospital outbreaks of norovirus. Early in an outbreak, symptomatic patients were cohorted in single rooms or bays in an attempt to contain the outbreak without closing the entire ward. Once a ward had been closed, and as beds became available through discharges, patients were decanted into single rooms or empty bays with doors to facilitate earlier cleaning and opening of affected areas on the same ward. The impact of these changes was assessed by comparing outbreak data for two periods before and after implementation of the new strategy.
Findings
Prior to June 2007, 90% of outbreaks were managed by closure of an entire ward, compared with only 54% from June 2007 onwards. The duration of closure was significantly shorter for bays compared with entire wards, both before (3.5 vs 6, P = 0.0327) and after (3 vs 5, P < 0.0001) June 2007. When considering all outbreaks, there was a significant reduction in duration of closure after the change in strategy (6 vs 5, P = 0.007).
Conclusion
Using ward compartmentalization to cohort affected patients at the beginning and end of norovirus outbreaks improved the efficiency of outbreak management and reduced operational disruption.
Noroviruses are small round structured viruses belonging to the Caliciviridae family and are a major cause of nosocomial gastroenteritis. Rapid spread of norovirus in healthcare establishments is facilitated by its low infectious dose, environmental stability, strain diversity and short-term immunity in affected individuals.
Hospital outbreaks are more common in the winter months and can have a significant operational and financial impact at a time when there is already an additional burden on services.
Clinical features may also be more protracted and severe in hospital patients, particularly in the immunocompromised and elderly with underlying chronic conditions.
In the past, national guidelines for managing hospital outbreaks of norovirus recommended ward closure as a central control measure, with reopening delayed until 72 h after the last symptomatic case.
Recently updated guidance for healthcare settings has suggested reducing this to 48 h after the resolution of symptoms in the last known case and at least 72 h after the initial onset of the last new case (http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1317131639453).
In response to problems in previous years we reviewed our outbreak management strategy in 2005 and introduced a number of measures, including rapid molecular testing for norovirus. Although this improved compliance with recommendations to close wards and contain outbreaks, it had little impact on the length of bed closure or the number of bed-days closed. In 2007, we reviewed our strategy again, and decided on a two-fold approach to limit the operational impact of outbreaks. First, soon after an outbreak had been identified, symptomatic patients were cohorted in single rooms or bays in an attempt to contain the outbreak without closing the entire ward. Second, when wards had been closed, and as beds became available through discharges, symptomatic or recovering patients were decanted into single rooms or empty bays with doors in order to facilitate earlier cleaning and opening of affected areas. The objective of this intervention study was to examine the effectiveness of this approach compared with the previous strategy, with particular evaluation of the impact on duration of bed closure and impact on bed-days closed.
Methods
Derriford Hospital is a 1200-bed teaching hospital in southwest England with 42 wards containing between 14 and 34 beds. Individual wards have between three and seven single rooms, with the remainder of beds configured in 5- or 6-bedded bays, at least two of which are fitted with doors. The infection prevention and control team (IPCT) consisted of 0.6 whole-time equivalent infection control doctors and 6.6 whole-time equivalent infection control nurses.
In this intervention study, data were collected prospectively on all hospital outbreaks of norovirus gastroenteritis between 1 June 2005 and 31 May 2011. Periods of June to the following May were selected to capture each seasonal epidemic. Norovirus outbreaks were defined as two or more cases of diarrhoea and/or vomiting affecting staff and/or patients in the same clinical area within 24 h of each other and where individual stool samples tested negative for other faecal pathogens and Clostridium difficile toxin and at least one tested positive for norovirus by a polymerase chain reaction (PCR) assay. PCR-based norovirus detection was introduced as a quality improvement measure in September 2005 and was performed using the single-tube reverse transcription PCR method described by Höhne and Schreier with automatic detection of fluorescence signal on an Applied Biosystems Prism 7000 Real time PCR machine.
Positive and negative samples were included in each run. Standard data collection was performed by the IPCT for each outbreak and included the numbers of symptomatic patients and staff, duration of the outbreak and number of bed-days closed. The latter was defined as the total number of beds closed, rather than just those that were unoccupied. Data are reported as median values, with interquartile ranges (IQRs) as shown in Table I, and analysed using a Kruskal–Wallis test. P ≤ 0.05 was considered significant. Pairwise comparisons, using a Wilcoxon rank sum test, were then carried out to compare duration of closure and bed-days closed between closure strategies and between study periods. P-values for pairwise comparisons were not adjusted for multiple comparisons. Analyses were performed using R, which is open-source software for statistical computing, analysis and graphics (available at http://www.r-project.org/).
These included closure of wards with reopening after the last affected patient had been asymptomatic for 72 h and terminal cleaning with Actichlor Plus (1000 ppm chlorine; Ecolab Ltd, Swindon, UK). After June 2007, as soon as the number of cases on a ward exceeded available single rooms, bays with symptomatic patients were closed. If patients in more than two bays were affected, then the entire ward was closed. As beds on closed wards became available through discharges, symptomatic and recovering patients, were decanted into single rooms or empty bays with doors on the same ward in order to facilitate earlier cleaning and opening of affected areas on the same ward. Empty bays were then cleaned with Actichlor Plus and either reopened or used to facilitate the cleaning of other bays when this was required. Gloves and aprons were worn for contact. In outbreak areas, hand washing was with soap and water. Staff segregation between affected and non-affected patients was practised where possible. When possible, bays with doors were used to cohort patients while other bays were cleaned in preparation for opening. If further cases occurred in the bay during the clean, this was suspended to allow a review of the situation. The clean was then either restarted after at least a further 24 h or when all patients had been moved out of the bay. Throughout the study period, strict protocols for hand hygiene, clinical practice, segregation of duties and environmental decontamination were reinforced on an annual basis through staff education and training, reissuing of an outbreak pack, minuted meetings for each outbreak and at least daily visits to affected wards by the IPCT. A relapse of an outbreak was defined as further cases of gastroenteritis occurring in the same clinical area within one week following completion of the clean and reopening.
Results
Monthly hospital norovirus outbreaks managed by bay or ward closure from June 2005 to May 2011 are shown in Figure 1. There were between 11 and 44 outbreaks per year and these occurred with a typical seasonal pattern, predominantly in the winter months. The severity of all outbreaks, as assessed by the median number of patients and staff affected, was similar before and after the change in strategy (see Table I). Prior to June 2007, 90% of outbreaks (36 of 40) were managed by closure of an entire ward, compared with only 54% (51 of 95) from June 2007 onwards.
Figure 1Monthly hospital norovirus outbreaks managed by ward (blue line) or bay (red line) closure, from June 2005 to May 2011. The solid black vertical line indicates the change in outbreak management strategy in June 2007. Dashed vertical lines indicate epidemic seasons.
The duration of closure of bays and wards before and after the change in strategy is shown in Figure 2, with median and IQR values given in Table I. There was a significant difference in the median duration of bed closure when comparing across study periods and management strategies (chi-squared = 26.21, P < 0.0001). Pairwise tests showed that the duration of closure was significantly shorter for bays as compared to entire wards, both before (3.5 vs 6, P = 0.0327) and after (3 vs 5, P < 0.0001) the change in outbreak management strategy. When considering all outbreaks, whether managed by bay or entire ward closure, there was a significant reduction in duration of closure after the change in strategy (6 vs 5, P = 0.007).
Figure 2Duration of bed closures, by study period (pre-intervention in the upper row, post-intervention in the lower row) and by outbreak management strategy (bay closures on the left, ward closures on the right). Dashed vertical lines denote median days closed.
The number of bed-days closed before and after the change in strategy is shown in Figure 3, with median and IQR values given in Table I. There was a significant difference in the median bed-days closed when comparing across study periods and management strategies (chi-squared = 76.3, P < 0.0001). Pairwise tests showed that the number of bed-days closed was significantly lower for bays compared with entire wards, both before (21 vs 199, P = 0.0013) and after (24 vs 170, P < 0.0001) the change in management strategy. For outbreaks managed by entire ward closure, there was also a significant decrease in bed-days closed between the study periods (199 before vs 170 after, P = 0.0273). When considering all outbreaks, whether managed by bay or entire ward closure, there was a significant decrease in bed-days closed after the change in strategy (180 vs 96, P < 0.0001).
Figure 3Number of bed-days lost, by study period (pre-intervention in the upper row, post-intervention in the lower row) and by outbreak management strategy (bay closures on the left, ward closures on the right). Dashed vertical lines denote median days closed.
Hospital managers were generally compliant with recommendations to close bays or wards and there were only three occasions during the entire study period when patients were admitted to a closed area for operational reasons. Relapses of infection, which were not linked to the presence of bay doors, occurred in two of the 36 outbreaks managed by entire ward closure before and in three of the 51 outbreaks following the change in outbreak management. Relapses of infection occurred in none of the four outbreaks managed by closure of bays before and in five of the 44 outbreaks after the change in strategy.
Discussion
Controlling nosocomial spread of norovirus is particularly challenging given its highly transmissible nature. Dissemination of the virus following vomiting or explosive diarrhoea will potentially expose other patients and staff in the same clinical area to the infectious agent and result in extensive environmental contamination.
While traditional containment through closure of wards and cleaning 72 h after the last symptomatic case may be effective, this approach can cause considerable operational disruption during extensive or prolonged outbreaks. The findings of our work provide support for a recent study showing that many norovirus outbreaks can be controlled by containment in bays rather than by entire ward closures, particularly when this is combined with adequate infection control support.
Using this approach we were able to manage 46% of norovirus outbreaks through containment in single rooms and bays and without closing an entire ward. To be effective, this approach needs to be implemented promptly and early in an outbreak before extensive transmission has occurred within a clinical area. It was possible to manage outbreaks affecting similar numbers of patients either by closure of bays alone or by closure of the entire ward. In general, it became necessary to close wards when symptomatic patients were distributed throughout the ward, rather than due to the magnitude of the outbreak.
An additional part of our revised strategy was to decant symptomatic or recovering patients on closed wards into single rooms or empty bays with doors as beds became available. This facilitated earlier terminal cleaning and opening of affected areas and also allowed individual bays to open while other areas of a ward remained closed to admissions and discharges. Adopting this strategy reduced the length of closure of entire wards as well as the number of bed-days closed. Entire wards that were closed after the change in strategy were those where control had not been possible by single room and bay containment, usually because of the distribution of symptomatic patients throughout the ward. These outbreaks were likely to be more complex than wards closed before this change occurred, for example requiring terminal cleaning of a more extensive area. Improved control was achieved after the change in strategy, despite the more complex nature of these outbreaks. In general, we found that as long as patients can be moved to single rooms or cohorted in bays with doors, it was not necessary to terminate a clean. When this did occur, the delay was included in the recorded duration of an outbreak and can be seen not to have had a major impact on this. Although there was a small rise in the number of relapses on wards that had been reopened after this strategy was introduced, this increase was not statistically significant. When considering all outbreaks, the two combined changes in management strategy had a significant impact on both the length of bed closures and bed-closure-days. As a result of this, we plan to install further bay doors in order to further facilitate norovirus containment. Even though relapses were not linked to the presence of bay doors, these represent an important visual and physical barrier.
Although a detailed economic analysis of the impact of the change in management strategy was not performed, it is reasonable to assume that shorter duration of closure and fewer bed-closure-days reduced the financial impact of outbreaks of norovirus on the hospital. Norovirus gastroenteritis detection was identical throughout the study period and therefore no additional microbiological diagnostic resource was required. Similarly, no additional IPCT staff were required to implement the new strategy. Although additional time was required to provide expert advice on the appropriate cohorting of patients, the resultant reduction in outbreak duration meant that less overall time was spent by infection control nurses on outbreak management. Containment of patients in single rooms or bays reduced the amount of additional cleaning required and in general we found that repeated terminal cleaning was not required due to relapses of infection. The most significant economic benefit would have been due to the shorter duration of outbreaks and the reduction in bed-days lost. The cost per inpatient bed-day has recently been estimated to be between £197 and £855 depending on clinical specialty.
Our strategy, which results in more rapid turnaround of closed areas and removal of restrictions on admissions and discharges, allows clinical services to return to full capacity in a shorter period of time. Over an entire outbreak season, the economic benefits are likely to be considerable.
The main limitation of this study is that we have been unable to quantify other factors that may have contributed to improved outbreak management, such as the degree of infection control support. Although the size of the IPCT increased over the study period, the number of infection control nurses dealing with outbreaks did not change, as additional staff were deployed on other duties such as surgical site surveillance. Although annual review of outbreak management and updating of the outbreak pack was performed, no further significant changes to practice were made during the study period. Due to the fact that we did not record the number of bed-days lost throughout the study period, we are unable to provide these data. Instead, we have provided the bed-days closed, which reflect the total number of beds closed rather than just those that were unoccupied. This is reasonable given that once an area was closed due to an outbreak, there were no admissions, transfers or discharges (other than to the patient's own home), effectively removing all the beds in the bay or ward from operational use, whether occupied or not. Finally, we are unable to provide a detailed analysis of the genotypes of norovirus circulating or on the immunity of the local population, both which may have affected outbreak severity.
In conclusion, this study provides further evidence that many outbreaks of norovirus in hospital can be managed by containment in single rooms and bays rather than by closure of entire wards. Using compartmentalization of wards to cohort remaining symptomatic and recovering patients on closed wards facilitates early terminal cleaning and opening of previously affected bays for normal operational use. This combined approach, in combination with strict infection control procedures, is effective in reducing the length and operational disruption of hospital norovirus outbreaks. Replication of these measures in other hospitals would be anticipated to lead to major operation and cost savings.
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