Excess mortality following community-onset norovirus enteritis in the elderly

Risk of Hospitalization and Mortality Following Medically Attended Norovirus Infection-Veterans Health Administration, 2010-2018

Background

While prior studies have suggested a role for norovirus gastroenteritis in contributing to severe morbidity and mortality, the importance of norovirus as a causal pathogen for hospitalization and mortality remains poorly understood. We estimated the effect of laboratory-confirmed norovirus infection on hospitalization and mortality among a national cohort of veterans who sought care within the Veterans Affairs health care system.

Methods

We analyzed electronic health record data from a cohort study of adults who were tested for norovirus within the Veterans Affairs system between 1 January 2010 and 31 December 2018. Adjusted risk ratios (aRRs) for hospitalization and mortality were estimated using log-binomial regression models, adjusting for age, Clostridioides difficile, underlying medical conditions, and nursing home residence.

Results

In total, 23 196 veterans had 25 668 stool samples tested for norovirus; 2156 samples (8.4%) tested positive. Testing positive for norovirus infection, compared with testing negative, was associated with a slight increased risk of hospitalization (aRR, 1.13 [95% confidence interval, 1.06-1.21]) and a significant increased risk of mortality within 3 days after the norovirus test (2.14 [1.10-4.14]). The mortality aRR within 1 week and 1 month were reduced to 1.40 (95% confidence interval, .84-2.34) and 0.97 (.70-1.35), respectively.

Conclusions

Older veterans with multiple comorbid conditions were at a slight increased risk of hospitalization and significant increased risk of mortality in the 3 days after a norovirus-positive test, compared with those testing negative. Clinicians should be aware of these risks and can use these data to inform clinical management for veterans with norovirus.

Risk factors for norovirus infection in healthcare workers during nosocomial outbreaks: a cross-sectional study

Background

Norovirus outbreaks cause severe medico-socio-economic problems affecting healthcare workers and patients. The aim of the study was to investigate prevalence of norovirus infection and risk factors for infection in healthcare workers during nosocomial outbreaks.

Methods

A cross-sectional study of norovirus infections in healthcare workers was performed in seven outbreak wards in a large university hospital. Packs (swab for rectal sampling, and questionnaire) were posted to healthcare workers on notification of a ward outbreak. Rectal samples were examined with norovirus-specific real-time PCR. Replies from questionnaires were analysed using logistic regression models with norovirus genogroup (G)II positive findings as dependent variable. The results are expressed as odds ratios (OR) with 95% confidence intervals (CI). Sequencing and phylogenetic analyses (1040 nucleotides) were used to characterize norovirus strains from healthcare workers. Cluster analyses included norovirus GII.4 strains detected in ward patients during the ongoing outbreaks.

Results

Of 308 packs issued to healthcare workers, 129 (42%) were returned. norovirus GII was detected in 26 healthcare workers (20.2%). Work in cohort care (OR 4.8, 95% CI 1.4–16.3), work in wards for patients with dementia (OR 13.2, 95% CI 1.01–170.7), and having diarrhoea, loose stools or other gastrointestinal symptoms the last week (OR 7.7, 95% CI 2.5–27.2) were associated with increased norovirus prevalence in healthcare workers. Sequencing revealed norovirus GII.4 in healthcare workers samples, and strains detected in healthcare workers and ward patients during a given ward outbreak showed ≥ 99% similarity.

Conclusion

Norovirus positive findings in healthcare workers were strongly associated with symptomatic infection, close contact with sick patients, and dementia nursing.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-021-00979-8.

What proportion of care home outbreaks are caused by norovirus? An analysis of viral causes of gastroenteritis outbreaks in care homes, North East England, 2016-2018

BACKGROUND

Outbreaks of infectious gastroenteritis are common in care homes for the elderly. Norovirus can cause these outbreaks, but diagnosis is frequently based solely on clinical characteristics. Our objective in this study was to describe the epidemiology of norovirus and other gastrointestinal pathogens in these settings.

METHODS

We analysed surveillance data from gastroenteritis outbreaks reported in North East England between 04 July 2016 to 01 July 2018. Stool samples taken during these outbreaks were tested for a range of viral and bacterial pathogens. We described the epidemiology of these outbreaks and explored the characteristics of norovirus outbreaks versus from other viral causes using multivariable logistic regression.

RESULTS

From the 566 care home gastroenteritis outbreaks in this study, we found that norovirus was the pathogen most frequently isolated. Norovirus was detected in 64% of outbreaks with a pathogen identified. Sapovirus was found in 13%; rotavirus in 11%. We found that norovirus outbreaks were associated with higher attack rates (aOR 1.03, 95% CI 1.01-1.05) and fewer cases sampled (aOR 0.74, 95% CI 0.60-0.91), compared to outbreaks caused by other viral pathogens.

CONCLUSIONS

These results are important as they quantify the contribution of norovirus to gastroenteritis outbreaks in care homes. Given this evidence, we emphasize the importance of non-specific outbreak interventions that can affect the impact of all such outbreaks. We further recommend that these findings are used to inform the implementation strategies of any norovirus-specific interventions such as a norovirus vaccine.

Prospective cohort study to investigate the burden and transmission of acute gastroenteritis in care homes: epidemiological results

OBJECTIVES

To estimate the incidence of gastroenteritis in individuals in care homes.

DESIGN

Prospective cohort study.

SETTING

Five participating care homes in North West England, UK.

PARTICIPANTS

Residents and staff present at the five study care homes between 15 August 2017 and 30 May 2019 (n=268).

OUTCOME MEASURES

We calculated incidence rates for all gastroenteritis cases per 1000 person-years at risk and per 1000 bed-days at risk. We also calculated the incidence rate of gastroenteritis outbreaks per 100 care homes per year.

RESULTS

In total 45 cases were reported during the surveillance period, equating to 133.7 cases per 1000 person-years at risk. In residents the incidence rate was 0.62 cases per 1000 bed-days. We observed seven outbreaks in all care homes included in surveillance, a rate of 76.4 outbreaks per 100 care homes per year. 15 stool samples were tested; three were positive for norovirus, no other pathogens were detected.

CONCLUSIONS

We found that surveillance of infectious gastroenteritis disease in care homes based on outbreaks, the current general approach, detected a majority of cases of gastroenteritis. However, if policymakers are to estimate the burden of infectious gastroenteritis in this setting using only routine outbreak surveillance data and not accounting for non-outbreak cases, this study implies that the total burden will be underestimated.

Burden of rotavirus infection in hospitalized elderly individuals prior to the introduction of rotavirus vaccination in Sweden

BACKGROUND

Rotavirus gastroenteritis (GE) in the elderly has been much less studied than in children.

OBJECTIVES

The aim of this study was to determine the morbidity and mortality for elderly hospitalized patients with rotavirus GE prior to the introduction of rotavirus vaccination in Sweden, and to investigate the epidemiology of rotavirus genotypes in these patients.

STUDY DESIGN

All patients 60 years or older who were hospitalized at Sahlgrenska University Hospital, Gothenburg, Sweden, and were rotavirus positive in a clinical diagnostic test from 2009 to 2016, were included. Medical records were reviewed and rotavirus genotyping real-time PCR was performed.

RESULTS

One hundred and fifty-nine patients were included, corresponding to an annual incidence of hospitalization due to rotavirus GE of 16/100 000 inhabitants aged 60 years or older. G2P[4] was the most common genotype, followed by G1P[8] and G4P[8]. The majority of patients had community-onset of symptoms and no or few pre-existing health disorders. Four patients (2.5%) died within 30 days of sampling. Patients with hospital-onset rotavirus GE had a longer median length of stay following diagnosis compared with patients with community-onset of symptoms (19 vs. 5 days, p = 0.001) and higher 30-day mortality (8.6% (3/35) vs. < 1% (1/124), p = 0.03).

CONCLUSIONS

Hospitalization due to rotavirus GE among the elderly seems to mainly affect otherwise healthy individuals and is associated with low 30-day mortality.

Norovirus and Other Viral Gastroenteritis

New and old entero-pathogenic viruses are increasing in the society and in the healthcare, like the Calicivirus family (Norovirus, Sapovirus, Astrovirus), Reovirus family (Rotavirus) (especially infant, toddler and elderly) and rarely other viral types such as adenovirus (especially serotype 40, 41), bocavirus, parechovirus, enterovirus and a variety of other types. In all types of gastroenteritis, infection prevention measures are performed as with norovirus, described below. The following chapter is focused on practical measures to detect and prevent transmission of entero-pathogenic viruses in healthcare institutions.

How timely closure can reduce outbreak duration: gastroenteritis in care homes in North West England, 2012-2016

Background

Data on outbreaks of infectious gastroenteritis in care homes have been collected using an internet-based surveillance system in North West England since 2012. We analysed the burden and characteristics of care home outbreaks to inform future public health decision-making.

Methods

We described characteristics of care homes and summary measures of the outbreaks such as attack rate, duration and pathogen identified. The primary analysis outcome was duration of closure following an outbreak. We used negative binomial regression to estimate Incidence Rate Ratios (IRR) and confidence intervals (CI) for each explanatory variable.

Results

We recorded 795 outbreaks from 379 care homes (37.1 outbreaks per 100 care homes per year). In total 11,568 cases, 75 hospitalisations and 29 deaths were reported. Closure within three days of the first case (IRR = 0.442, 95%CI 0.366–0.534) was significantly associated with reduced duration of closure. The total size of the home (IRR = 1.426, 95%CI = 1.275–1.595) and the total attack rate (IRR = 1.434, 95%CI = 1.257–1.595) were significantly associated with increased duration of closure.

Conclusions

Care homes that closed promptly had outbreaks of shorter duration. Care home providers, and those advising them on infection control, should aim to close homes quickly to prevent lengthy disruption to services.

Norovirus causing severe gastrointestinal disease following allogeneic hematopoietic stem cell transplantation: A retrospective analysis

BACKGROUND

Norovirus (NV) can cause chronic and severe gastroenteritis with possible lethal outcome in immunocompromised patients. The knowledge of NV infections in allogeneic hematopoietic stem cell transplantation (HSCT) recipients is limited. The aim of this study was to clarify the clinical importance of NV in a large cohort of HSCT recipients.

METHODS

All patients undergoing HSCT and diagnosed with NV at Karolinska University Hospital from 2006-2012 were included in the study (63 patients). Clinical data were collected from medical records, and statistics were performed using the logistic regression method.

RESULTS

The majority of patients (70%) had short-term symptoms (≤14 days). However, 54% of all patients required admission or prolonged hospitalization owing to the infection. In 16% of the patients the symptoms were chronic (>30 days), and in all but one of these patients the clinical picture also was severe, with malnutrition requiring long-term TPN, or serious dehydration. Severe combined immune deficiency (SCID) diagnosis was associated with chronic symptoms of NV infection (OR 30.3, CI 2.5-368).

CONCLUSION

NV is an important pathogen in the HSCT setting, although the infection seems to be mild in most patients. Increased knowledge is needed to further identify risk factors for a severe course of NV infection in HSCT patients.

The clinical features and infectious etiologies of acute diarrhea in immunocompromised hosts

Objectives The acute diarrhea is a common complaint among immunocompromised hosts, and may cause life threatening event. The infectious etiologies vary depending on virus, bacteria, and parasites. The most common etiology of acute gastroenteritis is known as enteric virus in Korea. But there are few studies about the infectious etiology of acute gastroenteritis in immunocompromised hosts. The aim of this study was to investigate the infectious etiologies of acute diarrhea in immunocompromised hosts. Methods Seventy three patients were enrolled prospectively in a university hospital from January 2013 to July 2014. Immunocompromised hosts included above 65-year-old people, patients with chronic diseases, solid organ or stem cell transplants, solid organ malignancies, hematologic malignancies, immunosuppressive or steroid taking patients. The clinical data were collected and stool samples collected during diarrhea were undergone laboratory analysis for enteric viruses and bacterial enteropathogens including Salmonella spp., Shigella spp., and Clostridium difficile. Results Fifty five patients were analyzed as follows : above 65 year-old people were 36 cases (66%), previous antibiotic usage was 22 cases (41.5%). 44 cases (81.1%) were admitted to general ward whereas 9 cases to ICU (17%). 41 cases (73.6%) were treated with antibiotics. Positive C. difficile toxin assays were 6 cases (11.9%). Other infectious etiologies were not found. Conclusions C. difficile infection was more common infectious etiology while enteric viruses and other bacteria are not associated with acute diarrhea among immunocompromised hosts in this study. So C. difficile infection must be considered preferentially in immunocompromised hosts with acute diarrhea.

Prospective cohort study to investigate the burden and transmission of acute gastroenteritis in care homes: a study protocol

INTRODUCTION

Noroviruses are the leading cause of acute gastroenteritis in all age groups, but illness is more severe and causes excess mortality in the elderly, particularly those in long-term care. The total burden of norovirus disease in the elderly in the UK is poorly defined; no current surveillance programmes systematically or accurately quantify norovirus infection in those living in care homes. The aim of this study is to evaluate an enhanced surveillance system for acute gastroenteritis among the elderly in care homes.

METHODS AND ANALYSIS

We will conduct this prospective cohort study in care homes in North West England; residents and staff at study care homes will be asked to participate. We will prospectively enrol a cohort of participants in an enhanced surveillance system to capture the incidence of acute gastroenteritis and use multiplex PCR to detect pathogens. We will sample symptomatic and non-symptomatic participants to understand characteristics of norovirus disease and susceptibility to infection. We will generate novel data on transmission dynamics by collecting data on the pattern of interactions within care homes using electronic proximity sensors. Comparisons of outbreak and non-outbreak periods will be used to quantify the impact of norovirus outbreaks on care homes.

ETHICS AND DISSEMINATION

The study has been approved by the North West-Greater Manchester South NHS Research Ethics Committee (REC Reference: 16/NW/0541). Study outputs will be disseminated through scientific conferences and peer-reviewed publications. This study will provide detailed insight on the burden and aetiology of acute gastroenteritis in care homes, in addition to generating novel data on transmission dynamics and risks. The study will identify areas for improving infection control practice and allow more accurate modelling of the introduction of interventions such as vaccination.

Norovirus Infections in Long-Term Care Facilities

Noroviruses have emerged as one of the leading causes of viral gastroenteritis worldwide, affecting community-dwelling and institutionalized older adults. Recent global epidemics present a growing challenge to the healthcare system and to long-term care facilities. Noroviruses spread readily and rapidly through multiple routes (e.g., person-to-person contact, contact with contaminated surfaces, airborne dissemination of vomitus) and thus are able to sustain an epidemic efficiently and successfully. Although norovirus gastroenteritis is a short self-limited illness in healthy immunocompetent individuals, it can result in significant morbidity and mortality in vulnerable compromised persons such as frail elderly persons and older residents of nursing homes. Diagnosis is made by clinical assessment and confirmed primarily by stool evaluation using polymerase chain reaction. Treatment is confined to supportive measures. Public health prevention and control strategies provide guidance regarding surveillance and the necessary steps to curb the clinical effect and spread of norovirus infections in various settings, including long-term care.

Occurrence of novel GII.17 and GII.21 norovirus variants in the coastal environment of South Korea in 2015

Human norovirus (HNoV), a positive-sense RNA virus, is the main causative agent of acute viral gastroenteritis. Multiple pandemic variants of the genogroup II genotype 4 (GII.4) of NoV have attracted great attention from researchers worldwide. However, novel variants of GII.17 have been overtaking those pandemic variants in some areas of East Asia. To investigate the environmental occurrence of GII in South Korea, we collected water samples from coastal streams and a neighboring waste water treatment plant in North Jeolla province (in March, July, and December of 2015). Based on capsid gene region C analysis, four different genotypes (GII.4, GII.13, GII.17, and GII.21) were detected, with much higher prevalence of GII.17 than of GII.4. Additional sequence analyses of the ORF1-ORF2 junction and ORF2 from the water samples revealed that the GII.17 sequences in this study were closely related to the novel strains of GII.P17-GII.17, the main causative variants of the 2014-2015 HNoV outbreak in China and Japan. In addition, the GII.P21-GII.21 variants were identified in this study and they had new amino acid sequence variations in the blockade epitopes of the P2 domain. From these results, we present two important findings: 1) the novel GII.P17-GII.17 variants appeared to be predominant in the study area, and 2) new GII.21 variants have emerged in South Korea.

Epidemiology of Acute Gastroenteritis Outbreaks Caused by Human Calicivirus (Norovirus and Sapovirus) in Catalonia: A Two Year Prospective Study, 2010-2011

Background

The epidemiology of cases of acute gastroenteritis (AGE) of viral etiology is a relevant public health issue. Due to underreporting, the study of outbreaks is an accepted approach to investigate their epidemiology. The objective of this study was to investigate the epidemiological characteristics of AGE outbreaks due to norovirus (NoV) and sapovirus (SV) in Catalonia.

Material and Methods

Prospective study of AGE outbreaks of possible viral etiology notified during two years in Catalonia. NoV and SV were detected by real time reverse transcription polymerase (RT-PCR).

Results

A total of 101 outbreaks were registered affecting a total of 2756 persons and 12 hospitalizations (hospitalization rate: 0.8x1,000,000 persons-year); 49.5% of outbreaks were foodborne, 45.5% person to person and 5% waterborne. The distribution of outbreaks according to the setting showed a predominance of catering services (39.6%), nursing homes and long term care facilities (26.8%) and schools (11.9%). The median number of cases per outbreak was 17 (range 2–191). The total Incidence rate (IR) was 18.3 per 100,000 persons-years (95%CI: 17.6–19.0). The highest IR was in persons aged ≥65 years (43.6x100,000 (95% CI: 41.0–46.2)) (p<0.001). A total of 1065 samples were analyzed with a positivity rate of 60.8%. 98% of positive samples were NoV (GII 56.3%; GI 4.2%; GII+GI 4.2%; non- typable 33.0%). SV was identified in two person-to-person transmission outbreaks in children.

Conclusions

These results confirm the relevance of viral AGE outbreaks, both foodborne and person-to-person, especially in institutionalized persons. SV should be taken into account when investigating viral AGE outbreaks.

Norovirus in symptomatic and asymptomatic individuals: cytokines and viral shedding

Noroviruses (NoV) are the most common cause of epidemic gastroenteritis world-wide. NoV infections are often asymptomatic, although individuals still shed large amounts of NoV in their stool. Understanding the differences between asymptomatic and symptomatic individuals would help in elucidating mechanisms of NoV pathogenesis. Our goal was to compare the serum cytokine responses and faecal viral RNA titres of asymptomatic and symptomatic NoV-infected individuals. We tested serum samples from infected subjects (n = 26; 19 symptomatic, seven asymptomatic) from two human challenge studies of GI.1 NoV for 16 cytokines. Samples from prechallenge and days 1-4 post-challenge were tested for these cytokines. Cytokine levels were compared to stool NoV RNA titres quantified previously by reverse transcription-polymerase chain reaction (RT-qPCR). While both symptomatic and asymptomatic groups had similar patterns of cytokine responses, the symptomatic group generally exhibited a greater elevation of T helper type 1 (Th1) and Th2 cytokines and IL-8 post-challenge compared to the asymptomatic group (all P < 0·01). Daily viral RNA titre was associated positively with daily IL-6 concentration and negatively with daily IL-12p40 concentration (all P < 0·05). Symptoms were not associated significantly with daily viral RNA titre, duration of viral shedding or cumulative shedding. Symptomatic individuals, compared to asymptomatic, have greater immune system activation, as measured by serum cytokines, but they do not have greater viral burden, as measured by titre and shedding, suggesting that symptoms may be immune-mediated in NoV infection.

A decade of norovirus disease risk among older adults in upper-middle and high income countries: a systematic review

BACKGROUND

Noroviruses (NoVs) are the most common cause of acute gastroenteritis (AGE) causing both sporadic and outbreak-associated illness. Norovirus (NoV) infections occur across all ages but certain sub-groups are considered at increased risk due to heightened transmission and/or symptom severity. Older adults are potentially at high risk of NoV-associated illness due to frequent outbreaks in long-term care facilities (LTCFs) and severe health outcomes following infection. Elucidation of NoV risk among older adults will support prevention, treatment and control efforts.

METHODS

We conducted a systematic literature review to summarize the published risk estimates of NoV-associated illness, hospitalization and death among individuals aged 65 years and older. A structured search using defined NoV and gastroenteritis (GE) terms was performed in the PubMed and EMBASE databases of human studies published between January 1, 2003 and May 16, 2013.

RESULTS

We identified 39 studies from high income (HI) and upper-middle income (UMI) countries. Thirty-six percent of publications provided risk estimates based on laboratory-confirmed or epidemiologically-linked population-based surveillance data using molecular diagnostic methods. Over the study period, estimated annual NoV rates and extrapolated number of cases among older adults in HI and UMI countries were: 29-120/10,000 or 1.2-4.8 million NoV-associated illnesses; 18-54/10,000 or 723,000-2.2 million NoV-associated outpatient visits; 1-19/10,000 or 40,00-763,000 NoV-associated inpatient visits; 0.04-0.32/10,000 or 2000-13,000 NoV-associated deaths. NoV was responsible for approximately 10-20 % of GE hospitalizations and 10-15 % of all-cause GE deaths among older adults. Older adults experienced a heightened risk of nosocomial infections. Those in LTCFs experience frequent NoV outbreaks and the range in attack rates was 3-45 %, case hospitalization rates 0.5-6 % and case fatality rates 0.3-1.6 %.

CONCLUSIONS

Older adults are at increased risk of severe NoV-associated health outcomes. NoV-associated hospitalization rates were higher, more severe, resulted in longer stays and incurred greater costs than for younger patients. NoV-associated mortality rates were approximately 200 % higher among individuals 65 years and older compared to <5 years. The burden of NoV among older adults is expected to rise along with societal aging and increased need for institutionalized care. NoV prevention in older adults, including potential vaccination, may significantly impact risk of severe illness.

Role of noroviruses as aetiological agents of diarrhoea in developing countries

Diarrhoea is considered to be the second leading cause of death due to infections among children  < 5 years of age worldwide that may be caused by bacteria, parasites, viruses and non-infectious agents. The major causative agents of diarrhoea in developing countries may vary from those in developed countries. Noroviruses are considered to be the most common cause of acute diarrhoea in both children and adults in industrialized countries. On the other hand, there is a lack of comprehensive epidemiological evidence from developing countries that norovirus is a major cause of diarrhoea. In these regions, asymptomatic norovirus infections are very common, and similar detection rates have been observed in patients with diarrhoea and asymptomatic persons. This review summarizes the current knowledge of norovirus infection in developing countries and seeks to position infections with noroviruses among those of other enteropathogens in terms of disease burden in these regions.

Norovirus in healthcare settings

Purpose of review

To provide an overview of the burden of norovirus disease in healthcare settings and the factors responsible for outbreaks in these institutions; to assess progress on interventions aimed at reducing the burden of norovirus disease.

Recent findings

Norovirus outbreaks in healthcare settings are driven by confluence of viral diversity, the built environment, and host factors. Some of these characteristics may be modifiable and the target of successful interventions.

Summary

Most norovirus outbreaks in hospital and residential care institutions are associated with a particular genotype, known as GII.4. The persistence of norovirus is associated with strain diversity, which is driven by immune evasion and viral adaptation to interaction with a variety of human histo-blood group antigens. The healthcare environment presents serious challenges for control, both because of the physical structure of the built space and the high levels of contact among patient populations who may have compromised hygiene. Increased vulnerability among the populations in healthcare institutions is likely to be multifactorial and may include the following: nutritional status, immunodeficiency or senescence, chronic inflammation, and microbiome alterations. Current control measures are based on general infection control principles, and treatment is mainly supportive and nonspecific. Vaccines and antiviral agents are being developed with promising results, but none are currently available.

Burden of norovirus in healthcare facilities and strategies for outbreak control

Norovirus is the most frequently occurring cause of community-acquired acute gastroenteritis in people of all ages. It is also one of the most frequent causes of outbreaks in healthcare settings, affecting both long-term care facilities and acute care hospitals. Whereas norovirus gastroenteritis is typically mild and resolves without medical attention, healthcare-associated infections often affect vulnerable populations, resulting in severe infections and disruption of healthcare services. Globally, most norovirus outbreaks in hospitals and residential care institutions are associated with genogroup II type 4 (GII.4) strains. Recent data demonstrate that excess mortality occurs during outbreak periods in healthcare facilities. Nosocomial outbreaks can result in large economic and societal costs. Current control measures for norovirus are largely based on general infection control principles, and treatment is mainly supportive and non-specific. While neither vaccines nor antiviral agents are currently available, both are being developed with encouraging results.

Evaluation of anamnestic criteria for the identification of patients with acute community onset viral gastroenteritis in the emergency department--A prospective observational study

BACKGROUND

To our knowledge no clinical criteria for the identification of community onset viral gastroenteritis in individual patients have been evaluated systematically with modern PCR-based diagnostic assays as gold standard.

OBJECTIVE

The aim of this study was to identify factors independently associated with the detection of virus by PCR in rectal swab samples from patients with acute community onset gastroenteritis.

METHODS

A prospective observational study was conducted from December 2010 through March 2011 at the emergency department (ED) of a large teaching hospital. All patients who reported vomiting and/or diarrhoea up to 48 h prior to their visit to the ED were asked to participate. A rectal swab sample was obtained from each patient. Symptoms, date of onset, and epidemiological data were recorded. Samples were analysed with a multiple real-time PCR targeting 6 viral agents (astrovirus, adenovirus, rotavirus, sapovirus, and norovirus GI and GII).

RESULTS

Two hundred and five patients fulfilled the inclusion criteria, of whom 66 agreed to participate; their median (IQR) age was 65 (38-84) y and 43 (65%) were females. Thirty-one (47%) were positive by PCR for at least 1 of the agents examined (26 norovirus, 2 sapovirus, 2 rotavirus, and 1 adenovirus). Diarrhoea and a short duration of symptoms (≤ 2 days) were independently associated with a positive rectal swab sample, with odds ratios of 7.5 (95% confidence interval (CI) 2.0-28) and 10.4 (95% CI 1.9-56), respectively (p < 0.01 for both). A multivariate model including these 2 variables had a sensitivity of 81% (25/31) and a specificity of 69% (24/35).

CONCLUSIONS

Diarrhoea and a short duration of symptoms were the only anamnestic criteria independently associated with acute community onset viral gastroenteritis confirmed by PCR.

Noroviruses and histo-blood groups: the impact of common host genetic polymorphisms on virus transmission and evolution

Noroviruses (NoVs) are recognized as a leading cause of human gastroenteritis worldwide. Infection occurs following the ingestion of contaminated food or, most often, through direct contact from person to person. However, not all individuals are equally sensitive to these viruses. Indeed, NoVs use glycans of the ABH and Lewis histo-blood group antigen family (HBGAs) as attachment factors. At the epithelial level, the synthesis of these HBGAs requires the action of several glycosyltransferases that are encoded by the ABO, FUT2, and FUT3 genes. The combined polymorphism at these three loci dictates sensitivity to NoV infection because the attachment profile to these glycans varies among strains. Structural analysis of the capsid protein interaction with HBGAs reveals distinct modes of binding for strains of genogroups I and II but high conservation within each genogroup, whereas minor amino acid changes are sufficient to generate modifications of HBGA-binding specificities or affinities. Such modifications therefore induce changes in the spectrum of susceptible individuals. Studies of NoV-HBGA interactions together with phylogenetic analyses and the epidemiologic survey of strains indicate that NoV transmission and evolution depend on both the establishment of herd immunity and the genetic resistance of many individuals, which confers herd innate protection by restricting NoV circulation.

Clinical characteristics of norovirus-associated deaths: a systematic literature review

Although deaths are often reported in the context of norovirus outbreaks, clinical and epidemiologic characteristics of the decedents prior to death are not well established. Through a literature review of published reports of deaths associated with norovirus infection, we identified and summarized 158 norovirus-associated deaths in 12 countries from 1988 to 2011.

[Genetic susceptibility to norovirus infection]

Norovirus (NoV) are the most common cause of acute gastroenteritidis in humans worldwide. They are transmitted through consumption of contaminated food, or mostly by direct person-to-person contact. However, susceptibility to NoV infection is variable. NoVs recognize carbohydrate ligand, including A, B, H and Lewis histoblood group antigen (HBGAs) for attachment to human epithelial cells. Synthesis of these HBGAs requires various glycosyltransferase encoded by the ABO, FUT2, FUT3 genes. The presence of distinct carbohydrates structures dependent upon the combined polymorphism at the FUT2, FUT3 and ABO loci influences susceptibility to NoV infection. NoV-glycan interactions studies show that different strains recognize specific HBGAs. Together with herd immunity, HBGAs play a major role in the epidemiology and evolution of NoVs.

Postinfectious gastrointestinal disorders following norovirus outbreaks

BACKGROUND

The US Centers for Disease Control and Prevention estimates 20.9 million norovirus infections annually in the United States. Although the acute disease burden is sizeable, emerging data suggest norovirus may be associated with chronic gastrointestinal problems. We identified known outbreaks in US military recruits and used the Defense Medical Encounter Database (DMED) to identify the risk of new onset functional gastrointestinal disorders (FGD) and gastroesophageal reflux disease (GERD).

METHODS

Subjects reporting for care of acute gastroenteritis (AGE) at a military treatment clinic during 3 known norovirus outbreaks were identified. Each AGE subject was matched with up to 4 subjects with unrelated medical encounters. Medical encounter data were analyzed for the duration of military service time (or a minimum of 1 year) to assess for incident FGD or GERD. Relative risks were calculated using regression models.

RESULTS

We identified 1718 subjects from 3 outbreaks. After controlling for important demographic covariates, the incidence of constipation, dyspepsia, and GERD was approximately 1.5-old higher (P < .01) in AGE-exposed subjects than matched subjects. We also noted variability in outcome incidence across outbreaks.

CONCLUSIONS

It appears that the risk of dyspepsia, constipation, and GERD are higher among those who have AGE during a confirmed norovirus outbreak. Although these findings need confirmation, they suggest that dysmotility may result subsequent to these infections. If confirmed, the costs and morbidity associated with the chronic consequences of norovirus should be considered.

Protruding domain of capsid protein is necessary and sufficient to determine murine norovirus replication and pathogenesis in vivo

Human noroviruses (HuNoVs) are the major cause of epidemic, nonbacterial gastroenteritis worldwide. Due to the lack of a tractable model system and the inability to grow HuNoVs in cell culture, factors required for the norovirus (NoV) life cycle and pathogenesis in the host remain largely unknown. The discovery of murine norovirus (MNV) and the development of reverse-genetics systems for this virus provide an opportunity to study these aspects of NoV infection in vitro and in vivo. Previous studies identified a single amino acid at residue 296 in the protruding (P) domain of the capsid protein that is responsible for determining the virulence of the MNV clone MNV1.CW1 in 12956/SvEv background STAT1-deficient (STAT1(-/-)) mice. In this report, we identified and characterized another determinant of lethality in the P domain that is necessary and sufficient to determine the replication and pathogenesis of the MNV clones MNV1.CW3 and CR6.STL1 in C57BL/6 background STAT1(-/-) mice. Furthermore, we describe how the role of residue 296 in MNV virulence differs between STAT1(-/-) mouse strains. We also describe potential interactions between subdomains of the P domain, as well as between other virus elements, which facilitate recovery of MNV using a reverse-genetics system.