Re-assessing the total burden of norovirus circulating in the United Kingdom population

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Norovirus is the commonest cause of GI disease in the UK.

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Less stringent diagnostic threshold Increases previous estimate by 26%.

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Re-assessed estimate equates to burden of infection at 59 per 1000 person years.

The second Infectious Intestinal Diseases study (IID2) estimated the incidence of norovirus in the UK at 47/1000 population (three million cases annually). Clinically significant norovirus was defined using a cycle threshold (ct) value of <30; a more stringent cut-off than used in diagnostic laboratories. The low infectious dose of norovirus means asymptomatic individuals potentially contribute to ongoing transmission. Using a less stringent but diagnostically relevant threshold increases the estimation of the population burden of norovirus infection by around 26% to 59/1000 person years (95% CI 52.32–64.98), equating to 3.7 million norovirus infections annually (3.3–4.1 million). With possible vaccines on the horizon for norovirus, having a good estimate of the total burden of norovirus infection, as well as symptomatic disease will be useful in helping to guide vaccination policy when candidate vaccines become available.

Shiga Toxin-Producing Escherichia coli O157, England and Wales, 1983-2012

Although incidence remained constant, outbreaks from contaminated meat and milk declined and those from petting farms and schools and nurseries increased.

We evaluated clinical Shiga toxin–producing Escherichia coli O157 infections in England and Wales during 1983–2012 to describe changes in microbiological and surveillance methods. A strain replacement event was captured; phage type (PT) 2 decreased to account for just 3% of cases by 2012, whereas PT8 and PT21/28 strains concurrently emerged, constituting almost two thirds of cases by 2012. Despite interventions to control and reduce transmission, incidence remained constant. However, sources of infection changed over time; outbreaks caused by contaminated meat and milk declined, suggesting that interventions aimed at reducing meat cross-contamination were effective. Petting farm and school and nursery outbreaks increased, suggesting the emergence of other modes of transmission and potentially contributing to the sustained incidence over time. Studies assessing interventions and consideration of policies and guidance should be undertaken to reduce Shiga toxin–producing E. coli O157 infections in England and Wales in line with the latest epidemiologic findings.

Early Experience with the Sydney and EVT Prostheses for Endoluminal Treatment of Abdominal Aortic Aneurysms

Purpose:

The aim of this study was to report early experiences with the Sydney and Endovascular Technologies (EVT) prostheses for the treatment of abdominal aortic aneurysms (AAA) deemed suitable for endoluminal tube graft repair.

Methods:

Consecutive endoluminal tube graft repairs were analyzed over the first 12 months in which the Sydney and EVT prostheses were used. Patients eligible for the EVT prosthesis had type I AAAs: a proximal neck length ≥ 2 cm, a distal cuff length ≥ 1.5 cm, and nontortuous iliac arteries ≥ 8 mm. Selection criteria for the Sydney device were more liberal and included AAAs that had distal cuffs < 1.5 cm. During the study period, 28 of 91 patients evaluated for AAA repair were thus selected for endoluminal grafting: 18 patients received the Sydney endograft and 10 the EVT device. Medical comorbidities were present in slightly less than one third of patients in both groups. Contrast-enhanced computerized tomography (CT) was performed preoperatively, within 10 days of operation, and at 6 and 12 months postprocedure.

Results:

All endografts were successfully deployed in both groups. Postprocedural CT scans revealed incomplete aneurysm exclusion in four patients with the Sydney endograft. Subsequent deployment of a second endograft sealed these “leaks” in two cases; the other two were converted to open repair (89% clinical success). No leaks were seen with the EVT device. Local/vascular complications occurred in 33% of the Sydney group compared with 20% for the EVT device (p = 0.001); systemic sequelae were more common in the EVT group (30% versus 17% in the Sydney cohort, p = 0.002). There were no deaths within 30 days; three late deaths were not procedure related.

Conclusion:

AAAs that are suitable for endoluminal tube graft repair may be treated with a high rate of initial success with either the Sydney or EVT prostheses. More liberal selection criteria may increase the likelihood of local/vascular complications.

Illusion-Destruction by Appropriate Scaling

The inappropriate constancy scaling theory of visual distortion illusions is tested by optically projecting typical models giving these figures by perspective. Appropriate or inappropriate stereoscopic disparities are then added–with the prediction that when perspective and stereo are geometrically correct the distortion should vanish. This is confirmed with measurements for the Müller-Lyer illusion and by observation of several other classical examples. It is suggested that much previous work has investigated ‘end stop’ conditions, given by angles too extreme to be generated as perspective. Conditions for appropriate scaling, giving zero or small distortions, are found to be critical but readily attainable.

A Prospective Study of Changes in Morphology and Dimensions of Abdominal Aortic Aneurysms following Endoluminal Repair: A Preliminary Report

Purpose:

The aim of this prospective study was to analyze early changes in morphology and dimensions of abdominal aortic aneurysms (AAA) following endoluminal repair.

Methods:

Forty-two of 62 patients undergoing endoluminal repair of AAAs between May 1992 and November 1994 were potentially available for follow-up at 6 months or longer after operation. After excluding patients with failed endoluminal repairs, patients who died within 6 months of operation, and patients with anastomotic aneurysms, a study group of 30 patients remained. Contrast-enhanced computed tomography (CE-CT) was performed preoperatively, within 10 days of operation, and at 6 and 12 months postprocedure. Based on the postoperative CE-CT findings, patients were divided into two groups: those with no extravasation of contrast into the aneurysmal sac (group I; n = 26), and those in which there was contrast extravasation (“leak”) into the aneurysmal sac (group II; n = 4).

Results:

The mean maximum diameters of AAAs in group I diminished progressively at 6 and 12 months, while those in group II increased. Twenty-three (88%) patients in group I had decreased diameter of AAA, while all patients in group II had progressive increase in AAA diameter. Patients who had an increase in AAA diameter had a significantly higher incidence of leak compared with those who had a decrease in diameter (p = 0.001).

Conclusions:

The majority of AAAs in which the sac has been excluded from the general circulation diminish in size following successful endoluminal repair. An increase in size occurs in those AAAs in which a communication exists between the aortic lumen and the sac. These results suggest that successfully excluded AAAs that continue to increase in size should be suspected of having an undetected leak.

Overt Visual Attention in Parkinson's Disease

The ability of Parkinsonian (PD) patients to control overt visual attention was investigated, by measuring reaction time to a visual stimulus presented at different distances (1.5 deg, 6 deg, and 12 deg) and directions (left or right) from a central fixation point. Prior to the onset of the target stimulus (a square), a cue stimulus appeared just above the fixation point. With equal probability, the arrow pointed to the left, or to the right, or was ambiguous (with two heads). On 20% of their presentations, the left and right arrows pointed in the direction opposite to where the target was to appear. Subjects were informed that 20% of cues would be misleading, and correcting lenses were used to optimise their visual acuity. In previous work with a similar paradigm, only one target eccentricity was used, and subjects were not refracted, leaving open the possibility that PD subjects had more difficulty in seeing the cues and targets.

The eight PD subjects had longer reaction times than age-matched normal controls (and were relatively slower for the more eccentric targets), but made fewer errors in all conditions. In particular, they were more accurate than the controls on the presentations when the cue was misleading or ambiguous, suggesting that the PD group were ignoring the cue. It seems unlikely that the subjects discriminate the direction of the cues, given the use of optical correction, and they reported seeing the cues. Our data are consistent with those of other workers who have described a similar ‘disengagement of attention’ in PD (Clark et al, 1989 Neuropsychologia27 131 – 140) and attributed it to decreased catecholaminergic activity following destruction of midbrain structures (Wright et al, 1990 Neuropsychologia28 151 – 159).

Fusion and Rivalry of Illusory Contours

The general question is raised: “Are visual contours given directly from striate-cortex feature-detector activity?‘’ Phenomena of ‘subjective’ or ‘cognitive’ contours are examined to challenge this view, on the ground that contours can be extrapolations across low-probability gaps. The contours may be curved and may have poor ‘gestalt’ qualities—so ‘gestalt closure’ is not appropriate, but may be a sub-class of these phenomena. It is suggested that these illusory contours (and brightness differences) are generated by perceptually postulated masking objects—these being part of perceptual ‘scene analysis strategy’, since strong evidence for nearer objects is provided by improbable gaps.

Experiments are reported, in which each eye is given a different ‘cognitive’ contour figure such that there are disparate but illusory contours. It is found that these are fused to give three-dimensional illusory. surfaces bowing in front of the display. Masking objects must be in front of gaps; what happens here with reversal of stereo depth? Switching the eyes often gives rivalry of the illusory contours when masking is incompatible with the stereo depth. Implications for normal stereo vision are discussed.

Endoluminal Repair of Abdominal Aortic Aneurysms: Strengths and Weaknesses of Various Prostheses Observed in a 4.5-Year Experience

Purpose:

To summarize the results of endovascular abdominal aortic aneurysm (AAA) treatment using several endograft designs over a 4.5-year experience and offer comparisons on the various devices.

Methods:

From May 1992 to August 1996, 121 AAA patients meeting the criteria for an endoluminal repair were treated with 1 of 5 endograft designs in three configurations. The endografts were implanted in the operating room under fluoroscopic control. Follow-up included contrast-enhanced computed tomography within 10 days of operation, 6 months postoperatively, and annually thereafter.

Results:

Endografts were successfully deployed in 106 patients (88%). Fifteen cases were converted to open repair. Six procedure-related deaths occurred within 30 days owing to myocardial infarction (3), combined renal failure and septicemia (2), and multisystem failure (1). There were 36 local/vascular complications (30%) and 18 systemic/remote complications (15%). Of the 121 patients undergoing endoluminal AAA repair, 93 (77%) are currently alive and well with their AAAs excluded from the circulation.

Conclusions:

Trends in endoluminal AAA repair and prosthetic design point toward simpler devices and earlier treatment of smaller aneurysms once the long-term outcome of aortic endografting has been determined.

Endoluminal Grafting of Abdominal Aortic Aneurysms: Causes of Failure and Their Prevention

Purpose:

The aim of this study was to analyze the causes of failure of endoluminal grafting for abdominal aortic aneurysms (AAA) and to put forward proposals for preventing these failures.

Methods:

Since May 1992, endoluminal repair of aneurysms was undertaken in 47 patients. Forty-three of these patients had AAAs and are the basis of this study. All procedures were nonurgent and were performed in the operating room with the patient draped for an open repair in the event of failed endoluminal repair. Radiographic guidance was used to pass the endografts into the aorta via a delivery sheath introduced through the femoral or iliac arteries. The configuration of the endografts was tubular (n = 28), tapered aortoiliac/aorto-femoral (n = 11), and bifurcated (n = 4).

Results:

Successful endoluminal repair was achieved in 34 of 43 (79%) patients. The remaining nine were terminated in favor of an open repair. The causes of failure were problems with access (2), balloon malfunction (1), stent dislodgment (3), graft thrombosis (1), and inability to deploy the contralateral limb of a bifurcated graft (2). All failed endoluminal repairs proceeded to successful open repair. There was no perioperative mortality in patients undergoing endoluminal repair or in those whose endoluminal repair was converted to open operation.

Conclusions:

The failures of endoluminal grafting have been analyzed. Methods of avoiding access problems, balloon malfunction, and stent dislodgment have been defined and recommendations made.

Three-Year Experience with the White-Yu Endovascular GAD Graft for Transluminal Repair of Aortic and Iliac Aneurysms

Purpose:

To report a > 3-year experience with a modular, balloon-expandable endovascular graft used for aneurysm exclusion in the aorta and other arteries.

Methods:

The customized White-Yu Endovascular GAD Graft, a woven polyester prosthesis with an intrinsic Elgiloy wire graft attachment system along the body of the graft, is a flexible endograft design available in straight, tapered, and bifurcated versions that can be delivered transluminally through 18F to 24F sheaths.

Results:

Since July 1993, 93 patients have received the White-Yu endograft for treatment of 76 abdominal aortic, 3 thoracic aortic, 13 iliac, and 1 popliteal aneurysms. Of the 79 aortic procedures, 39 involved straight tube grafts, 20 were tapered aortoiliac models, and 20 were bifurcated devices. Success rates for tube grafts were 81% in the abdominal aorta and 100% for the thoracic aorta; 5 primary endoleaks (14%) and 2 conversions to surgery (5.6%) occurred with this graft type. Aortoiliac grafts were deployed successfully in 95% (19/20) of cases with 1 conversion (5%) due to thrombosis. Seventy-five percent of the bifurcated endograft procedures were successful, with 4 conversions (20%) for technical failures and 1 graft thrombosis. Four additional endografts were deployed to treat two primary and two secondary endoleaks in tube graft patients. Two access-related arterial injuries were treated surgically. There was one case of embolus to the distal femoral artery but no microembolization. Overall perioperative (30-day) mortality was 3.1%. Over a mean 18-month follow-up (range 2 to 39), no late graft thrombosis, stenosis, or graft migration has been seen on CT scans or X ray. Endoleak has not been detected in any aortoiliac or bifurcated graft. Aneurysm size has diminished consistently in successfully treated cases.

Conclusions:

The White-Yu endograft appears to offer a safe, efficacious, and minimally invasive means of excluding aneurysms from the circulation. Improvements in patient selection, surgical techniques, and equipment have reduced the incidence of endoleak and conversion to open repair over the course of the evaluation.

Shortening of Endografts during Deployment in Endovascular AAA Repair

Purpose:

To evaluate the incidence and extent of length changes during implantation of endovascular grafts in a prospective study of patients undergoing endovascular abdominal aortic aneurysm (AAA) repair.

Methods:

Data regarding the occurrence of intraoperative technical difficulties and device complications were recorded prospectively for the Vanguard or AneuRx self-expanding, bifurcated endovascular grafts in 64 patients (56 males; mean age 75 years). Graft length was measured in the sheath system before deployment and again immediately after deployment by fluoroscopic comparison to a graduated marking catheter.

Results:

Graft shortening ≥ 15 mm was documented in 22 (56%) of 39 Vanguard cases and 11 (44%) of 25 AneuRx endografts. Additional extension grafts were required to correct endoleak caused by inadequate graft length in 9 (14%) patients, but no conversion to open repair was necessary.

Conclusions:

There appears to be a high incidence of intraprocedural graft shortening with 2 current designs of self-expanding endoluminal grafts.

Norovirus Surveillance: An Epidemiological Perspective

Surveillance for norovirus is challenging because the nature of illness due to norovirus is such that the majority of people who are infected will not have any contact with medical services and are highly unlikely to have a sample collected for diagnosis. Public health advice urges people to not visit hospitals or their family physicians, to prevent the risk further spread. The recognition of the importance of this pathogen was quickly established following the introduction of surveillance of outbreaks of gastrointestinal infection in England and Wales in 1992. This period saw >1800 outbreaks of norovirus infection reported in hospitals in England, affecting >45 000 patients and staff. A new system for reporting outbreaks of norovirus infection in hospitals, the Hospital Norovirus outbreak Reporting Scheme (HNORS), began in January 2009. Summary information on outbreaks is provided by infection control staff at hospitals and includes questions on the date the first and last person in the outbreak became symptomatic and whether closure of a bay or ward was needed. In the first 3 years (2009-2011) of the HNORS surveillance scheme, 4000 outbreaks were reported, affecting 40 000 patients and 10 000 staff. Over the last 3 years, these outbreaks have been associated with an average of 13 000 patients and 3400 staff becoming ill, with 15 000 lost bed-days annually. With the possible introduction of a vaccine on the horizon, targeted research with a more integrated approach to laboratory testing and outbreak reporting is essential to a greater understanding of the epidemiology of norovirus.