Clinical manifestation of norovirus gastroenteritis in health care settings

Fitting outbreak models to data from many small norovirus outbreaks

Infectious disease often occurs in small, independent outbreaks in populations with varying characteristics. Each outbreak by itself may provide too little information for accurate estimation of epidemic model parameters. Here we show that using standard stochastic epidemic models for each outbreak and allowing parameters to vary between outbreaks according to a linear predictor leads to a generalized linear model that accurately estimates parameters from many small and diverse outbreaks. By estimating initial growth rates in addition to transmission rates, we are able to characterize variation in numbers of initially susceptible individuals or contact patterns between outbreaks. With simulation, we find that the estimates are fairly robust to the data being collected at discrete intervals and imputation of about half of all infectious periods. We apply the method by fitting data from 75 norovirus outbreaks in health-care settings. Our baseline regression estimates are 0.0037 transmissions per infective-susceptible day, an initial growth rate of 0.27 transmissions per infective day, and a symptomatic period of 3.35 days. Outbreaks in long-term-care facilities had significantly higher transmission and initial growth rates than outbreaks in hospitals.

The development of Web-based surveillance provides new insights into the burden of norovirus outbreaks in hospitals in England

A new surveillance system for outbreaks of norovirus in English hospitals, the hospital norovirus outbreak reporting system (HNORS), was launched in January 2009. On site investigators were enabled to enter data on outbreaks of norovirus directly onto a tailored system via an Internet-based front end. A standard dataset was designed to collect information describing the key epidemiological characteristics of each outbreak. In the period 1992-2008, 1817 suspected and confirmed outbreaks of norovirus in English hospitals were reported to national surveillance. After introduction of the new system there were 3980 reports of outbreaks of suspected and confirmed norovirus received in the years 2009-2011. Data from the new reporting system demonstrates that transmission of norovirus levies a heavy burden on English hospitals. On average, reported outbreaks are associated with 13,000 patients and 3400 staff becoming ill, 8900 days of ward closure and the loss of over 15,500 bed-days annually.

Monitoring of Calicivirus among day-care children: evidence of asymptomatic viral excretion and first report of GI.7 Norovirus and GI.3 Sapovirus in Brazil

Caliciviruses (Norovirus and Sapovirus) are important causes of acute gastroenteritis, with Norovirus (NoV) considered the leading cause of epidemic non-bacterial acute gastroenteritis; however, molecular and epidemiological data of the circulating Calicivirus (CV) strains among day-care children are still considered scarce. The role of asymptomatic CV excretion on viral transmission also remains poorly understood. The aim of the present study was to monitor the occurrence of NoV and Sapovirus (SaV) in a day-care center and to describe the molecular epidemiology of the circulating strains. Genomic sequencing and phylogenetic analysis of the capsid region were carried out in CV positive samples obtained from children younger than 5 years, with or without diarrhea, between October 2009 and October 2011. A total of 539 fecal samples were screened for CV. Forty-three (8%) were positive for NoV and 25 (4.6%) for SaV. Surprisingly, positivity rates for CV were significant in asymptomatic children, and virus circulation was detected in every month of the study. Great genomic diversity of CV was observed, and the circulating NoV strains were: GII.6, GII.2, GII.1, GI.7, GII.4, and GI.1. The SaV genotypes GI.1 and GI.3 were also detected. Five CV outbreaks caused by distinct viral strains were documented. This study provides an insight on the genetic diversity of CV in a day-care in Central West Brazil, highlighting the probable role of asymptomatic viral excretion and the significance of semi-closed settings in the dissemination of these agents.

Role of norovirus in acute gastroenteritis in the Northwest of Spain during 2010-2011

A total of 2,643 samples from patients with gastroenteritis in Galicia (NW Spain) were tested for the presence of Norovirus (NoV). NoV genogroup GI was detected in 416 (15.7%) samples, while NoV genogroup GII was detected in 278 (10.5%) samples. Mixed infections of NoV GI and GII were observed in 53 (2%) samples. Total prevalence of NoV in the analyzed samples was 28.3%. Besides NoV diagnosis assay, all the specimens were also submitted to routine clinical bacteriology tests. Cryptosporidium spp. as well as adenovirus (AdV) and rotavirus (RV) were determined on some samples after specific request by hospital units. The results obtained allowed to determine the disease etiology in 14.4% of the patients. Taking into account all the microorganisms studied, the etiological agent was determined for 39.5% of the cases. The results indicated that NoVs are the leading cause of acute gastroenteritis in all age-groups in Northwestern Spain, and that the lack of routine NoV diagnosis contributes to the underestimation of the importance of this virus, not only in outbreaks, but also in sporadic cases of acute gastroenteritis.

Concurrent outbreaks with co-infection of norovirus and Clostridium difficile in a long-term-care facility

We describe an outbreak of simultaneous Clostridium difficile and norovirus infections in a long-term-care facility. Thirty patients experienced acute gastroenteritis, and four had co-infection with identical C. difficile 027 and genotype II.4 New Orleans norovirus strains. Co-occurring infection requires improved understanding of risk factors, clinical impact, and testing strategies.

Surveillance definitions of infections in long-term care facilities: revisiting the McGeer criteria

(See the commentary by Moro, on pages 978-980 .) Infection surveillance definitions for long-term care facilities (ie, the McGeer Criteria) have not been updated since 1991. An expert consensus panel modified these definitions on the basis of a structured review of the literature. Significant changes were made to the criteria defining urinary tract and respiratory tract infections. New definitions were added for norovirus gastroenteritis and Clostridum difficile infections.

Clinical and molecular epidemiologic analyses of norovirus-associated sporadic gastroenteritis in adults from Beijing, China

Noroviruses (NoVs) are a major cause of nonbacterial acute gastroenteritis. The molecular epidemiology of NoV infections in China has not been well characterized. To study the incidence of NoV infections and the nature of the circulating NoV genotypes, 403 specimens were collected from adult outpatients with acute gastroenteritis in Beijing, China, between October 2007 and September 2008. Samples were examined for NoV by reverse transcriptase-polymerase chain reaction (RT-PCR) and sequences corresponding to both the NoV polymerase and capsid regions were characterized. Among the 403 specimens, 48 (11.9%) were positive for NoV and 1/3 NoV-associated gastroenteritis cases occurred during the colder months (November and December). Based on polymerase region sequences, 6 NoV genotypes (GII-4, GII-b, GII-6, GI-2, GI-3, and GI-4) were identified with GII-4 2006b being the most predominant genotype (37/48, 77.1%). Eleven distinct genotype sequences in polymerase and capsid regions were identified, indicating a genetic diversity among NoV isolates. This study suggested NoVs were an important pathogen responsible for sporadic acute gastroenteritis in adults in Beijing, China.

Norovirus diagnostics: options, applications and interpretations

Noroviruses are a frequent cause of both acute gastroenteritis and outbreaks of gastroenteritis. Infection is usually self-limiting although it has been associated with mortality in children in the developing world and in vulnerable groups such as immunodeficient or immunosuppressed and elderly patients elsewhere. Diagnostic tests may be useful in preventing or limiting the spread and duration of outbreaks, and are needed to define norovirus-associated morbidity and mortality. However, the interpretation of test results should take account of the limitations of the different tests currently available. Therefore, the clinical, immunological and molecular tests available for norovirus detection have been reviewed. Early recognition of cases (clinical diagnoses) together with confirmation by sensitive and specific laboratory tests may contribute to reducing the spread of norovirus within hospitals. Syndromic testing that includes multiple or multiplex assays for the detection of viral, bacterial and parasitic pathogens with the inclusion of control groups are likely to better define norovirus-associated morbidity and mortality in low- and middle-income countries.

Unrecognized norovirus infections in health care institutions and their clinical impact

Noroviruses (NoVs) have emerged as the leading cause of acute viral gastroenteritis (GE) in humans. Although diagnostic facilities have greatly improved, significant underdiagnosis of NoV in hospitals may still occur, thereby increasing clinical burden and nosocomial spread. We evaluated the underdiagnosis of sporadic NoV infections in a tertiary care hospital and estimated its clinical impact. From December 2008 until July 2009, fecal samples specifically referred for bacterial but not viral examination were retrospectively tested for NoV by real-time PCR. The clinical and virological data from patients with undiagnosed NoV infection (missed patients) were evaluated and compared with those from patients with recognized NoV. During the study period, 45 patients with undiagnosed NoV were detected, whereas 50 patients were regularly diagnosed. The missed NoV cases were more frequently adults than children (80% versus 46%; P < 0.001). The viral load levels did not differ between the diagnosed and missed patients, but missed patients more frequently presented without diarrhea (20% versus 4%; P < 0.07). The newly admitted missed NoV cases with GE underwent more diagnostic imaging (24% versus 4%; P < 0.01) and tended to be hospitalized longer. When missed-NoV patients were included, the number of nosocomial clusters doubled and missed patients were index cases in 5 of the 6 clusters. These data indicate that NoV infections are frequently missed despite routine laboratory testing and demonstrate that underdiagnosis of NoV patients is associated with costly abdominal imaging and nosocomial clustering. Awareness of NoV infection in adult patients and education about the importance of viral GE should be increased.

Compartmentalization of wards to cohort symptomatic patients at the beginning and end of norovirus outbreaks

BACKGROUND

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.

Nosocomial diarrhea: evaluation and treatment of causes other than Clostridium difficile

Diarrhea is common among hospitalized patients but the causes are distinct from those of diarrhea in the community. We review existing data about the epidemiology of nosocomial diarrhea and summarize recent progress in understanding the mechanisms of diarrhea. Clinicians should recognize that most cases of nosocomial diarrhea have a noninfectious etiology, including medications, underlying illness, and enteral feeding. Apart from Clostridium difficile, the frequency of infectious causes such as norovirus and toxigenic strains of Clostridium perfringens, Klebsiella oxytoca, Staphylococcus aureus, and Bacteroides fragilis remains largely undefined and test availability is limited. Here we provide a practical approach to the evaluation and management of nosocomial diarrhea when tests for C. difficile are negative.

The estimated disease burden of norovirus in The Netherlands

Noroviruses are an important cause of acute gastroenteritis in humans. We incorporated new insights gained over the past decade in an updated estimate of the disease burden of (foodborne) norovirus illness in The Netherlands in 2009. The disease outcomes - non-consulting cases, visiting a general practitioner, hospitalization and mortality - and the foodborne proportion were derived from cohort studies, surveillance data and literature. Age-specific incidence estimates were applied to the population age distribution in The Netherlands in 2009. The general population incidence was 3800/100 000 (95% CI 2670–5460), including 0.4 fatal cases/100 000,resulting in 1622 (95% CI 966–2650) disability-adjusted life-years in a population of 16.5 million [corrected].The updated burden of norovirus is over twofold higher than previously estimated, due in particular to the new insights in case-fatality ratios. Results suggest that the burden of norovirus institutional outbreaks is relatively small compared to the burden of community-acquired norovirus infections.

The roles of Clostridium difficile and norovirus among gastroenteritis-associated deaths in the United States, 1999-2007

BACKGROUND

Globally, gastroenteritis is recognized as an important contributor to mortality among children, but population-based data on gastroenteritis deaths among adults and the contributions of specific pathogens are limited. We aimed to describe trends in gastroenteritis deaths across all ages in the United States and specifically estimate the contributions of Clostridium difficile and norovirus.

METHODS

Gastroenteritis-associated deaths in the United States during 1999-2007 were identified from the National Center for Health Statistics multiple-cause-of-death mortality data. All deaths in which the underlying cause or any of the contributing causes listed gastroenteritis were included. Time-series regression models were used to identify cause-unspecified gastroenteritis deaths that were probably due to specific causes; seasonality of model residuals was analyzed to estimate norovirus-associated deaths.

RESULTS

Gastroenteritis mortality averaged 39/1000000 person-years (11 255 deaths per year) during the study period, increasing from 25/1 000 000 person-years in 1999-2000 to 57/1 000 000 person-years in 2006-2007 (P < .001). Adults aged ≥ 65 years accounted for 83% of gastroenteritis deaths (258/1 000 000 person-years). C. difficile mortality increased 5-fold from 10/1 000 000 person-years in 1999-2000 to 48/1 000 000 person-years in 2006-2007 (P < .001). Norovirus contributed to an estimated 797 deaths annually (3/1 000 000 person-years), with surges by up to 50% during epidemic seasons associated with emergent viral strains.

CONCLUSIONS

Gastroenteritis-associated mortality has more than doubled during the past decade, primarily affecting the elderly. C. difficile is the main contributor to gastroenteritis-associated deaths, largely accounting for the increasing trend, and norovirus is probably the second leading infectious cause. These findings can help guide appropriate clinical management strategies and vaccine development.

Severe outcomes are associated with genogroup 2 genotype 4 norovirus outbreaks: a systematic literature review

BACKGROUND

Noroviruses (NoVs) are the most common cause of epidemic gastroenteritis; however, the relative impacts of individual factors underlying severe illness are poorly understood. This report reviews published NoV outbreak reports to quantify hospitalization and mortality rates and assess their relationship with outbreak setting, transmission route, and strain.

METHODS

Using a string of terms related to "norovirus" and "outbreak," we 2435 nonduplicate articles identified in PubMed, EMBASE, and Web of Knowledge published between January 1993 and June 2011. Inclusion criteria included outbreaks with a minimum of 2 ill persons with a common exposure and at least 1 reverse-transcription polymerase chain reaction-confirmed case of NoV disease. Univariate analyses were performed, and multivariable models were fitted to estimate the independent effect of each factor.

RESULTS

We analyzed 843 NoV outbreaks reported in 233 published articles from 45 countries. Based upon 71724 illnesses, 501 hospitalizations, and 45 deaths, overall hospitalization and mortality rates were 0.54% and 0.06%, respectively. In multivariate analysis, genogroup 2 genotype 4 (GII.4) NoV strains were associated with higher hospitalization (incidence rate ratio [IRR], 9.4; 95% confidence interval [CI], 6.1-14.4; P< .001) and mortality rates (IRR, 3.1; 95% CI, 1.3-7.6; P = .01). Deaths were much more likely to occur in outbreaks occurring in healthcare facilities (IRR, 60; 95% CI, 6-109; P = .01).

CONCLUSIONS

Our review suggests that hospitalizations and deaths were more likely in outbreaks associated with GII.4 viruses, independent of other factors, and underscores the importance of developing vaccines against GII.4 viruses to prevent severe disease outcomes.

Molecular epidemiology of norovirus in Edinburgh healthcare facilities, Scotland 2007-2011

Norovirus (NoV) is a leading cause of outbreaks of gastroenteritis worldwide, and a major burden for healthcare facilities. This study investigated the NoV genotypes responsible for outbreaks in Edinburgh healthcare facilities between June 2008 and July 2011, and studied their temporal distribution to enable a better understanding of the epidemiology of the outbreaks. A total of 287 samples positive for NoV genogroup II (GII) RNA by reverse transcription-polymerase chain reaction (RT-PCR) during routine diagnostic testing were investigated. Nested RT-PCR (nRT-PCR) and sequencing was used to genotype the NoV strains. Overall, a total of 69 NoV strains belonging to six different genoclusters (GII.1, GII.2, GII.3, GII.4, GII.6, GII.13) were detected. The predominant genotype was GII.4 that included four variants, GII.4 2006a, GII.4 2006b, GII.4 2007 and GII.4 2010. Importantly, increases in NoV activity coincided with the emergence of new GII.4 strains, highlighting the need for an active surveillance system to allow the rapid identification of new strains.

Risk of infection following a visit to the emergency department: a cohort study

BACKGROUND

The risk of infection following a visit to the emergency department is unknown. We explored this risk among elderly residents of long-term care facilities.

METHODS

We compared the rates of new respiratory and gastrointestinal infections among elderly residents aged 65 years and older of 22 long-term care facilities. We used standardized surveillance definitions. For each resident who visited the emergency department during the study period, we randomly selected two residents who did not visit the emergency department and matched them by facility unit, age and sex. We calculated the rates and proportions of new infections, and we used conditional logistic regression to adjust for potential confounding variables.

RESULTS

In total, we included 1269 residents of long-term care facilities, including 424 who visited the emergency department during the study. The baseline characteristics of residents who did or did not visit the emergency department were similar, except for underlying health status (visited the emergency department: mean Charlson Comorbidity Index 6.1, standard deviation [SD] 2.5; did not visit the emergency department: mean Charlson Comorbidity index 5.5, SD 2.7; p < 0.001) and the proportion who had visitors (visited the emergency department: 46.9%; did not visit the emergency department: 39.2%; p = 0.01). Overall, 21 (5.0%) residents who visited the emergency department and 17 (2.0%) who did not visit the emergency department acquired new infections. The incidence of new infections was 8.3/1000 patient-days among those who visited the emergency department and 3.4/1000 patient-days among those who did not visit the emergency department. The adjusted odds ratio for the risk of infection following a visit to the emergency department was 3.9 (95% confidence interval 1.4-10.8).

INTERPRETATION

A visit to the emergency department was associated with more than a threefold increased risk of acute infection among elderly people. Additional precautions should be considered for residents following a visit to the emergency department.

Novel surveillance network for norovirus gastroenteritis outbreaks, United States

TOC Summary: The launch of CaliciNet in March 2009 was a milestone.

CaliciNet, the outbreak surveillance network for noroviruses in the United States, was launched in March 2009. As of January 2011, twenty state and local health laboratories had been certified to submit norovirus sequences and epidemiologic outbreak data to CaliciNet. During the network’s first year, 552 outbreaks were submitted to CaliciNet, of which 78 (14%) were associated with foodborne transmission. A total of 395 (72%) outbreaks were typed as GII.4, of which 298 (75%) belonged to a new variant, GII.4 New Orleans, which first emerged in October 2009. Analysis of the complete capsid and P2 region sequences confirmed that GII.4 New Orleans is distinct from previous GII.4 variants, including GII.4 Minerva (2006b).

Epidemiology and costs associated with norovirus outbreaks in NHS Lothian, Scotland 2007-2009

Healthcare-associated gastroenteritis outbreaks are becoming more common and are recognized challenges in hospital and community settings. In Edinburgh [NHS (National Health Service) Lothian], all the hospitals and the community were actively monitored for outbreaks of gastroenteritis from September 2007 to June 2009. In total, 1732 patients and 599 healthcare staff were affected in 192 unit outbreaks. In the acute sector, 1368 patients (0.99 cases/1000 inpatient bed-days) and 406 healthcare staff (0.29 cases/1000 inpatient bed-days) were affected in 155 unit outbreaks (0.23 unit outbreaks/day). Noroviruses were detected in 142 outbreaks (74%); 50 were not laboratory confirmed but were presumed to be noroviruses on epidemiological grounds. The closure of affected units to new admissions resulted in the loss of 3678 bed-days. By extrapolation, lost bed-days and staff absence due to gastroenteritis outbreaks cost NHS Lothian £1.2 million for the two norovirus seasons. Outbreaks in which the affected unit was closed within the first three days of recognizing the index case were contained in a mean of six days, and outbreaks in units that were closed later persisted for a mean of seven days; this difference was not statistically significant. Rapid implementation of control measures was effective in the control of outbreaks.

Norovirus gastroenteritis successfully treated with nitazoxanide

Infectious diarrhea is a common occurrence in the immunosuppressed population. We present a 43-year-old individual with large-volume stool output Norovirus acute gastroenteritis in the setting of relapsed refractory acute myelogenous leukemia, hematopoietic stem cell transplantation, and biopsy-proven cutaneous and pulmonary graft-versus-host disease. Therapeutic options such as intravenous immunoglobulin or reduction of immunosuppressants were not a feasible choice. A prompt clinical cure was achieved with nitazoxanide, a broad-spectrum antimicrobial agent. Nitazoxanide may be a safe therapeutic alternative, in which a reduction in immunosuppression may not be a viable option.

Chronic norovirus infection in pediatric hematopoietic stem cell transplant recipients: a cause of prolonged intestinal failure requiring intensive nutritional support

Norovirus infection is a major cause of nonbacterial gastroenteritis. In immunocompetent individuals the illness caused by norovirus is mostly self limiting. Excretion of norovirus has been reported to be prolonged in the immunocompromised including adult HSCT recipients. We report a case series of 13 children who received HSCT and required prolonged parenteral and enteral nutrition due to severe gut dysfunction accompanying protracted norovirus excretion that was monitored by RT-PCR. The median duration of viral excretion was 150 days (range 60-380) and the eventual clearance of norovirus from feces was closely associated with donor T cell recovery in the peripheral blood. There was no disease manifestation beyond the gut but the severity and length of norovirus associated illness suggests that HSCT should be delayed where possible in patients excreting the virus prior to conditioning therapy.

Economic impact of outbreaks of norovirus infection in hospitals

Norovirus is highly infectious and can spread rapidly in healthcare settings, consuming resources and resulting in longer hospital stays. Although the economic impact of specific past outbreaks has been reported (eg, a 2007 outbreak of norovirus infection at Johns Hopkins Hospital cost an estimated $650,000), these costs may not be generalizable. We developed an economic computer simulation model to assist policy makers, hospital administrators, infection control professionals, and other healthcare workers in determining how much to invest in norovirus prevention and control interventions above and beyond existing infection control measures.

Chronic diarrhea associated with persistent norovirus excretion in patients with chronic lymphocytic leukemia: report of two cases

BACKGROUND

Chronic diarrhea in patients treated with immunosuppressive agents or suffering from immunosuppressive disease can represent a diagnostic and therapeutic challenge to the clinician. Norovirus infection, a major cause of acute epidemic diarrhea, has been described as a cause of chronic diarrhea in patients who are immunosuppressed, including transplant recipients and the very young.

CASE PRESENTATIONS

We describe two patients, a 64 year-old man and a 59 year-old woman, both suffering from chronic lymphocytic leukemia and hypogammaglobulinemia, who developed chronic diarrhea resistant to therapy. In both cases, after months of symptoms, persistent norovirus infection--documented by repeatedly-positive high-sensitivity stool enzyme immunoassay--was found to be the cause. Both patients died with active diarrheal symptoms.

CONCLUSIONS

We describe the first cases of advanced chronic lymphocytic leukemia to suffer from chronic symptomatic norovirus infection. Clinicians caring for such patients, particularly those with concomitant hypogammaglobulinema, who have chronic unexplained diarrhea, should consider norovirus infection in the differential diagnosis.

Norovirus - a serious threat to business continuity for hospitals

Norovirus is a small RNA virus which causes the majority of outbreaks of infectious diarrhoea and vomiting. Outbreaks can occur in many settings including schools, military camps, cruise ships, hotels and hospitals. In the winter 2009-2010 surveillance in the UK revealed an increase in hospital outbreaks. Such outbreaks cause distress and discomfort to patients, and have the potential to cause serious disruption to the normal working of hospitals. This article describes some of the ways in which norovirus can disrupt a hospital’s normal business, and the consequences of such disruption. The case for investing in norovirus control is compelling.

Use of alcohol-based hand sanitizers as a risk factor for norovirus outbreaks in long-term care facilities in northern New England: December 2006 to March 2007

BACKGROUND

During December 2006 to March 2007, a substantial increase in norovirus illnesses was noted in northern New England. We sought to identify institutional risk factors for norovirus outbreaks in northern New England long-term care facilities (LTCFs).

METHODS

State health departments in Maine, New Hampshire, and Vermont distributed surveys to infection preventionists at all LTCFs in their respective states. We collected information regarding facility attributes, routine staff use of alcohol-based hand sanitizer (ABHS) versus soap and water, facility cleaning practices, and occurrence of any acute gastroenteritis outbreaks during December 2006 to March 2007. Norovirus confirmation was conducted in public health laboratories. Data were analyzed with univariate and logistic regression methods.

RESULTS

Of 160 facilities, 91 (60%) provided survey responses, with 61 facilities reporting 73 outbreaks; 29 were confirmed norovirus. Facilities reporting that staff were equally or more likely to use ABHS than soap and water for routine hand hygiene had higher odds of an outbreak than facilities with staff less likely to use ABHS (adjusted odds ratio, 6.06; 95% confidence interval: 1.44-33.99).

CONCLUSION

This study suggests that preferential use of ABHS over soap and water for routine hand hygiene might be associated with increased risk of norovirus outbreaks in LTCFs.

Norovirus gastroenteritis causes severe and lethal complications after chemotherapy and hematopoietic stem cell transplantation

Norovirus (NV) infections are a frequent cause of gastroenteritis (GE), but data on this disease in immunocompromised patients are limited. We analyzed an NV outbreak, which affected immunosuppressed patients in the context of chemotherapy or HSCT. On recognition, 7 days after admission of the index patient, preventive measures were implemented. Attack rates were only 3% (11/334) and 10% (11/105) among patients and staff members, respectively. The median duration of symptoms was 7 days in patients compared with only 3 days in staff members (P = .02). Three patients died of the NV infection. Commonly used clinical diagnostic criteria (Kaplan-criteria) were unsuitable because they applied to 11 patients with proven NV-GE but also to 15 patients without NV-GE. With respect to the therapeutic management, it is important to differentiate intestinal GVHD from NV-GE. Therefore, we analyzed the histopathologic patterns in duodenal biopsies, which were distinctive in both conditions. Stool specimens in patients remained positive for NV-RNA for a median of 30 days, but no transmission was observed beyond an asymptomatic interval of 48 hours. NV-GE is a major threat to patients with chemotherapy or HSCT, and meticulous measures are warranted to prevent transmission of NV to these patients.

Economic value of norovirus outbreak control measures in healthcare settings

Although norovirus is a significant cause of nosocomial viral gastroenteritis, the economic value of hospital outbreak containment measures following identification of a norovirus case is currently unknown. We developed computer simulation models to determine the potential cost-savings from the hospital perspective of implementing the following norovirus outbreak control interventions: (i) increased hand hygiene measures, (ii) enhanced disinfection practices, (iii) patient isolation, (iv) use of protective apparel, (v) staff exclusion policies, and (vi) ward closure. Sensitivity analyses explored the impact of varying intervention efficacy, number of initial norovirus cases, the norovirus reproductive rate (R(0)), and room, ward size, and occupancy. Implementing increased hand hygiene, using protective apparel, staff exclusion policies or increased disinfection separately or in bundles provided net cost-savings, even when the intervention was only 10% effective in preventing further norovirus transmission. Patient isolation or ward closure was cost-saving only when transmission prevention efficacy was very high (≥ 90%), and their economic value decreased as the number of beds per room and the number of empty beds per ward increased. Increased hand hygiene, using protective apparel or increased disinfection practices separately or in bundles are the most cost-saving interventions for the control and containment of a norovirus outbreak.

Increasing rates of gastroenteritis hospital discharges in US adults and the contribution of norovirus, 1996-2007

BACKGROUND

Diarrhea remains an important cause of morbidity, but until the mid 1990s, hospital admissions for diarrhea in the US adult population were declining. We aimed to describe recent trends in gastroenteritis hospitalizations and to determine the contribution of norovirus.

METHODS

We analyzed all gastroenteritis-associated hospital discharges during 1996-2007 from a nationally representative data set of hospital inpatient stays. Annual rates of discharges by age were calculated. Time-series regression models were fitted using cause-specified discharges as explanatory variables; model residuals were analyzed to estimate norovirus- and rotavirus-associated discharges. We then calculated the annual hospital charges for norovirus-associated discharges.

RESULTS

Sixty-nine percent of all gastroenteritis discharges were cause-unspecified and rates increased by ≥ 50% in all adult and elderly age groups (≥ 18 years of age) from 1996 through 2007. We estimate an annual mean of 71,000 norovirus-associated hospitalizations, costing $493 million per year, with surges to nearly 110,000 hospitalizations per year in epidemic seasons. We also estimate 24,000 rotavirus hospitalizations annually among individuals aged ≥ 5 years.

CONCLUSIONS

Gastroenteritis hospitalizations are increasing, and we estimate that norovirus is the cause of 10% of cause-unspecified and 7% of all-cause gastroenteritis discharges. Norovirus should be routinely considered as a cause of gastroenteritis hospitalization.

Norovirus: changing epidemiology, changing virology. The challenges for infection control

Norovirus infection is the commonest cause of outbreaks and sporadic cases of acute gastrointestinal disease in England and Wales. It is estimated that 4.5% of the population are infected by norovirus each year. Some years see more infections than others and occasionally peaks of summer time activity can occur. Current surveillance of norovirus is based on two main sources of information, routine laboratory reporting and reports of norovirus outbreaks. There are still significant barriers impeding a better understanding of the biology and epidemiology of noroviruses. Modern genetic techniques have shed light on ways in which the virus interacts with its host and evades the immune system. Some of these techniques have also led to new tools that may be useful in tracking outbreaks of norovirus, and in turn, to study the effect of potential intervention strategies, aimed at preventing or curtailing transmission within outbreaks.

Norovirus disease associated with excess mortality and use of statins: a retrospective cohort study of an outbreak following a pilgrimage to Lourdes

Although norovirus infection is generally known to be a mild disease, there is some evidence for severe outcome. An outbreak in a Dutch psychiatric institution, originating from pilgrims returning from Lourdes (France), provided an opportunity for performing a retrospective cohort study in order to identify risk factors for norovirus disease and excess mortality. Relative risks (RR) including 95% confidence intervals (CI) showed that attending the pilgrimage (RR 2·0, 95% CI 1·4–3·0) and age >70 (RR 1·7, 95% CI 1·2–2·2) were risk factors for symptomatic infection. In a subset of patients, for whom more detailed information was available, the use of statins was associated with norovirus disease when adjusted for underlying condition (adjusted odds ratio 3·9, 95% CI 1·2–13·0). Mortality was higher in cases infected during the pilgrimage compared to other residents (RR 20·9, 95% CI 4·7–93·8). Norovirus disease can lead to severe outcome. The newly identified risk of statins for contracting norovirus disease may have considerable consequences for the Western world and needs prospective confirmation.

Norovirus gastroenteritis

Recent epidemiologic studies have shown that norovirus is one of the most frequent causes of acute nonbacterial gastroenteritis. Reverse-transcription polymerase chain reaction and nucleotide sequencing are the means by which the hundreds of norovirus strains have been identified, named, and classified into genogroups and genetic clusters. They are also the means by which a particular strain is traced from the source of an outbreak throughout its spread. These molecular techniques have been combined with classic epidemiology to investigate norovirus outbreaks in diverse settings, including hospitals, nursing homes, dining locations, schools, daycare centers, and vacation venues. Outbreaks are difficult to control because of the apparent ease of transmission through food, water, person-to-person contact, and environmental surfaces. Almost all patients with norovirus gastroenteritis recover completely, but hospital and nursing home outbreaks have been associated with morbidity and mortality. The diagnostic and management approach to an individual patient is to use clinical and epidemiologic findings to rule out "not norovirus." At the first sign that there is an outbreak, strict compliance with cleaning, disinfection, and work release guidelines is important to prevent further spread.

Characteristics of norovirus gastroenteritis outbreaks in a psychiatric centre

Noroviruses are an important aetiological agent of acute gastroenteritis. They are responsible for large outbreaks of disease in the community, hospitals and long-term-care facilities. The clinical manifestations of norovirus outbreaks in psychiatric units are rarely described. The disease burden and impact highlight the importance of timely notification and investigation of these outbreaks. We analysed the characteristics of four norovirus outbreaks which occurred during a 3-year period in an in-patient psychiatric care unit. A total of 184 patients were affected which included 172 hospitalized patients, seven healthcare workers (HCWs) and five psychiatric nursing-home residents. The mean incidence rate of norovirus gastroenteritis (NVG) in hospitalized patients during these outbreaks was 12·7%. These outbreaks were characterized by higher incidence in middle-aged male patients, predominant sickness of diarrhoea, short duration of illness, peaks in late winter and early spring, and higher susceptibility in acute psychiatric patients. HCWs had longer duration of illness than psychiatric patients. More than 10% of affected patients experienced ≥ 2 infections. Infection control measures were instituted and a comprehensive, responsive standard operating procedure for NVG and outbreak management was developed. After implementation of these measures, no further outbreaks of NVG occurred during the study period.

Epidemiological and clinical features of norovirus gastroenteritis in outbreaks: a population-based study

Noroviruses are the most frequent cause of acute gastroenteritis in the community. In Catalonia, it is not clear how this type of viral gastroenteritis is evolving, and the objective of this prospective population-based study was to describe the incidence and epidemiological and clinical features of outbreaks of acute gastroenteritis due to norovirus in Catalonia between October 2004 and October 2005. Incidence rates were calculated using the estimated population of Catalonia in 2005. For each outbreak, the mode of transmission, the number of persons affected, demographic variables, clinical presentation, the date and time of onset of symptoms and the duration of symptoms, physician visits and hospitalizations were collected. Sixty viral outbreaks affecting 1791 people were identified, with no distinct seasonality. The mean number of outbreaks per month was 4.6. The global incidence was 24.6 per 100 000 person-years. The incidence was higher in women (25.7 per 100 000 person-years) and in the 5-11 years (52.4 per 100 000 person-years) and > or =65 years (42.4 per 100 000 person-years) age groups. The prevalence of vomiting, abdominal pain and general malaise was higher in children and adolescents, whereas the prevalence of diarrhoea and myalgia was higher in adults. These results suggest that norovirus infection has an important public health impact in Catalonia and that prevention strategies should be designed and implemented.

Pathogenesis of noroviruses, emerging RNA viruses

Human noroviruses in the family Caliciviridae are a major cause of epidemic gastroenteritis. They are responsible for at least 95% of viral outbreaks and over 50% of all outbreaks worldwide. Transmission of these highly infectious plus-stranded RNA viruses occurs primarily through contaminated food or water, but also through person-to-person contact and exposure to fomites. Norovirus infections are typically acute and self-limited. However, disease can be much more severe and prolonged in infants, elderly, and immunocompromised individuals. Norovirus outbreaks frequently occur in semi-closed communities such as nursing homes, military settings, schools, hospitals, cruise ships, and disaster relief situations. Noroviruses are classified as Category B biodefense agents because they are highly contagious, extremely stable in the environment, resistant to common disinfectants, and associated with debilitating illness. The number of reported norovirus outbreaks has risen sharply since 2002 suggesting the emergence of more infectious strains. There has also been increased recognition that noroviruses are important causes of childhood hospitalization. Moreover, noroviruses have recently been associated with multiple clinical outcomes other than gastroenteritis. It is unclear whether these new observations are due to improved norovirus diagnostics or to the emergence of more virulent norovirus strains. Regardless, it is clear that human noroviruses cause considerable morbidity worldwide, have significant economic impact, and are clinically important emerging pathogens. Despite the impact of human norovirus-induced disease and the potential for emergence of highly virulent strains, the pathogenic features of infection are not well understood due to the lack of a cell culture system and previous lack of animal models. This review summarizes the current understanding of norovirus pathogenesis from the histological to the molecular level, including contributions from new model systems.

Noroviruses - State of the Art

Noroviruses are a common cause of both endemic and epidemic gastroenteritis. These highly infectious viruses usually cause self-limited disease, but chronic infections occur in highly immunocompromised patients and unusual manifestations are also being described in some populations. Histoblood-group antigen expression is now recognized as an important susceptibility factor for many norovirus strains, but a correlate of acquired immunity to infection or illness has not yet been identified. Currently, treatment and prevention strategies rely on non-specific measures. However, virus-like particles containing capsid antigens are undergoing evaluation as a vaccine candidate for illness prevention. This article reviews the biologic properties, epidemiology, clinical features, host susceptibility, diagnosis, and treatment and prevention of norovirus infection.

Utility of clinical-epidemiological profiles in outbreaks of foodborne disease, Catalonia, 2002 through 2006

The objective of this study was to evaluate the use of clinical-epidemiological profiles for classifying non-laboratory-confirmed outbreaks of foodborne disease (FBD) in Catalonia between 2002 and 2006 and for elucidating associations among factors contributing to these outbreaks. A total of 275 nonfamily outbreaks were studied, of which 190 (69.1%) were laboratory confirmed and 85 (30.9%) were not. In 176 (92.6%) of laboratory-confirmed outbreaks and 69 (81.2%) of non-laboratory-confirmed outbreaks, information was obtained on contributing factors (P = 0.009). In 72% of non-laboratory-confirmed outbreaks, the etiology was assigned by using clinical-epidemiological profiles; thus, 93% of outbreaks eventually were associated with an etiology. In laboratory-confirmed outbreaks, poor personal hygiene was positively associated with norovirus (odds ratio [OR], 2.69; 95% confidence interval [CI], 1.47 to 4.89; P = 0.0007) and negatively associated with Salmonella and Campylobacter (OR, 0.54; 95% CI, 0.33 to 0.89; P = 0.01), and an unsafe source was positively associated with Salmonella and Campylobacter (OR, 4.07; 95% CI, 1.72 to 10.09; P = 0.001) and negatively associated with norovirus (OR, 0.14; 95% CI, 0.04 to 0.58; P = 0.001). No differences were found among contributing factors associated with outbreaks with a laboratory-confirmed etiology and those associated with outbreaks with an etiology assigned according to the clinical-epidemiological profiles. Clinical-epidemiological profiles are useful for determining what prevention and control strategies are appropriate to the agents involved in each community and for designing outbreak investigations.