Emergence of the GII-4 Norovirus Sydney2012 strain in England, winter 2012-2013

Norovirus is the commonest cause of acute gastrointestinal disease and is the main aetiological agent of outbreaks of gastroenteritis, particularly in semi-closed environments. Norovirus infections in England typically peak between December and March each year. The most commonly detected norovirus strains belong to the genetically diverse genogroup-II genotype-4 (GII-4) genocluster and in the previous two norovirus winter seasons the majority of GII-4 strains in circulation worldwide have been genetically similar to the GII-4 strain New Orleans 1805/2009/USA. At the beginning of the 2012/13 season a genetically distinct GII-4 strain (Sydney 2012/NSW0514/2012/AU) was described which emerged worldwide during the winter of 2012/13. Here we describe the emergence of norovirus strains genetically related to Sydney2012 in England during the 2012/13 season to replace NewOrleans2009 strains as the most commonly detected variant of GII-4 norovirus in England. Furthermore, we demonstrate that whilst the emergence of Sydney2012 coincided with an early peak in the number of norovirus outbreaks, there was not an overall increase in norovirus activity compared to the previous season. Finally, we show that the Sydney2012 strain is associated with distinct genetic changes compared to the NewOrleans2009 strain, and these changes may have contributed to the emergence of the Sydney2012 strain.

Visual problems in Parkinson's disease: A questionnaire survey

A questionnaire was completed by 53 putative sufferers from Parkinson's disease and 31 putative age-matched normal controls. The aim of the questionnaire was to elicit reports of any changes in visual perception. The incidence of self-reported Parkinsonian symptoms was very much higher in the patient group than in the controls. The patients reported significantly more problems with depth and motion perception than the controls. They also reported a significantly higher incidence of hallucinations, double vision and the need to turn the head to see objects in the periphery. However, the reported incidence of changes in brightness, colour, shape and size perception was not significantly different in the two groups. The results are discussed with reference to laboratory studies of Parkinsonian vision and to the likely neurological basis of some of the changes.

To close or not to close? Analysis of 4 year's data from national surveillance of norovirus outbreaks in hospitals in England

OBJECTIVE

To assess the impact of ward or bay closures, specifically, whether prompt closure of an affected ward shortens the duration of norovirus outbreaks and the resulting disruption in hospitals.

DESIGN

Analysis of summary data from hospitals on outbreaks of norovirus from 2009 to 2012.

METHODS

Using a large outbreak surveillance dataset, we examined the duration of outbreaks, duration of disruption, ward closures, the number of patients and staff affected and the number of lost bed-days, as functions of the timing of closure. We conducted Quasi-Poisson regression analyses to assess the effect of ward closure (timing of closure) on outcome measures, controlling for time of year (winter or summer), ward size and ward type (elderly care wards).

RESULTS

Regression analysis indicates that after controlling for season ward size and type, the duration of outbreak and duration of disruption were shorter, fewer patients were affected by the time of closure and fewer patients were affected overall, when closure occurred promptly (within 3 days of the first case becoming ill) compared with non-prompt closure groups. However, in outbreaks where wards were not closed, the length of outbreaks were similar to the prompt closure group and also had fewer patients and staff affected and fewer cases per day of outbreak compared with prompt closure.

CONCLUSIONS

Closing a bay or ward promptly in an outbreak of norovirus leads to a shorter duration of outbreaks, a shorter duration of disruption and fewer patients being affected compared with outbreaks where wards were not promptly closed. However, the interpretation of these results is not straightforward. The outbreaks where the ward was not closed at all have similar characteristics in terms of the duration of outbreak and fewer people were affected compared with the baseline prompt closure group.

Intermittent, posture-dependent, and late endoleaks after endovascular aortic aneurysm repair

In this article we present our experience with the concept of the unstable aortic sac after endovascular aortic aneurysm repair. The improvements in ultrasound technology and features suggestive of sac instability are described. Patients with this condition are usually considered to have endotension, in which the aortic sac undergoes progressive enlargement in the absence of any demonstrable endoleak. We have found, however that approximately one third of these patients have intermittent or posture-dependent endoleaks. The secondary ultrasound manoeuvres that enable these endoleaks to be diagnosed are described. An awareness of the potential presence of these endoleaks may avoid unnecessary conversion to open repair or late rupture.

Does spatial proximity drive norovirus transmission during outbreaks in hospitals?

OBJECTIVE

To assess the role of spatial proximity, defined as patients sharing bays, in the spread of norovirus during outbreaks in hospitals.

DESIGN

Enhanced surveillance of norovirus outbreaks between November 2009 and November 2011.

METHODS

Data were gathered during 149 outbreaks of norovirus in hospital wards from five hospitals in two major cities in England serving a population of two million. We used the time between the first two cases of each outbreak to estimate the serial interval for norovirus in this setting. This distribution and dates of illness onset were used to calculate epidemic trees for each outbreak. We then used a permutation test to assess whether proximity, for all outbreaks, was more extreme than would be expected by chance under the null hypothesis that proximity was not associated with transmission risk.

RESULTS

65 outbreaks contained complete data on both onset dates and ward position. We estimated the serial interval to be 1.86 days (95% CI 1.6 to 2.2 days), and with this value found strong evidence to reject the null hypothesis that proximity was not significant (p<0.001). Sensitivity analysis using different values of the serial interval showed that there was evidence to reject the null hypothesis provided the assumed serial interval was less than 2.5 days.

CONCLUSIONS

Our results provide evidence that patients occupying the same bay as patients with symptomatic norovirus infection are at an increased risk of becoming infected by these patients compared with patients elsewhere in the same ward.

Direct and indirect effects of rotavirus vaccination: comparing predictions from transmission dynamic models

Early observations from countries that have introduced rotavirus vaccination suggest that there may be indirect protection for unvaccinated individuals, but it is unclear whether these benefits will extend to the long term. Transmission dynamic models have attempted to quantify the indirect protection that might be expected from rotavirus vaccination in developed countries, but results have varied. To better understand the magnitude and sources of variability in model projections, we undertook a comparative analysis of transmission dynamic models for rotavirus. We fit five models to reported rotavirus gastroenteritis (RVGE) data from England and Wales, and evaluated outcomes for short- and long-term vaccination effects. All of our models reproduced the important features of rotavirus epidemics in England and Wales. Models predicted that during the initial year after vaccine introduction, incidence of severe RVGE would be reduced 1.8–2.9 times more than expected from the direct effects of the vaccine alone (28–50% at 90% coverage), but over a 5-year period following vaccine introduction severe RVGE would be reduced only by 1.1–1.7 times more than expected from the direct effects (54–90% at 90% coverage). Projections for the long-term reduction of severe RVGE ranged from a 55% reduction at full coverage to elimination with at least 80% coverage. Our models predicted short-term reductions in the incidence of RVGE that exceeded estimates of the direct effects, consistent with observations from the United States and other countries. Some of the models predicted that the short-term indirect benefits may be offset by a partial shifting of the burden of RVGE to older unvaccinated individuals. Nonetheless, even when such a shift occurs, the overall reduction in severe RVGE is considerable. Discrepancies among model predictions reflect uncertainties about age variation in the risk and reporting of RVGE, and the duration of natural and vaccine-induced immunity, highlighting important questions for future research.