Economic value of norovirus outbreak control measures in healthcare settings

Lessons from past pandemics: a systematic review of evidence-based, cost-effective interventions to suppress COVID-19

BACKGROUND

In an unparalleled global response, during the COVID-19 pandemic, 90 countries asked 3.9 billion people to stay home. Yet other countries avoided lockdowns and focused on other strategies, like contact tracing. How effective and cost-effective are these strategies? We aimed to provide a comprehensive summary of the evidence on past pandemic controls, with a focus on cost-effectiveness.

METHODS

Following PRISMA guidelines, MEDLINE (1946 to April week 2, 2020) and EMBASE (1974 to April 17, 2020) were searched using a range of terms related to pandemic control. Articles reporting on the effectiveness or cost-effectiveness of at least one intervention were included.

RESULTS

We found 1653 papers; 62 were included. The effectiveness of hand-washing and face masks was supported by randomized trials. These measures were highly cost-effective. For other interventions, only observational and modelling studies were found. They suggested that (1) the most cost-effective interventions are swift contact tracing and case isolation, surveillance networks, protective equipment for healthcare workers, and early vaccination (when available); (2) home quarantines and stockpiling antivirals are less cost-effective; (3) social distancing measures like workplace and school closures are effective but costly, making them the least cost-effective options; (4) combinations are more cost-effective than single interventions; and (5) interventions are more cost-effective when adopted early. For 2009 H1N1 influenza, contact tracing was estimated to be 4363 times more cost-effective than school closure ($2260 vs. $9,860,000 per death prevented).

CONCLUSIONS AND CONTRIBUTIONS

For COVID-19, a cautious interpretation suggests that (1) workplace and school closures are effective but costly, especially when adopted late, and (2) scaling up as early as possible a combination of interventions that includes hand-washing, face masks, ample protective equipment for healthcare workers, and swift contact tracing and case isolation is likely to be the most cost-effective strategy.

A recombinase polymerase amplification-based lateral flow strip assay for rapid detection of genogroup II noroviruses in the field

Human norovirus is the leading cause of viral gastroenteritis worldwide. Rapid detection facilitates management of disease outbreaks, but field diagnosis is difficult to achieve due to the lack of reliable and portable methods. Recombinase polymerase amplification (RPA) is a robust isothermal amplification method that is capable of rapidly amplifying and detecting nucleic acids using simple equipment. In this study, RPA combined with lateral flow (LF) strips specific for human genogroup II (GII) noroviruses was established and evaluated. The assay specifically detects purified GII noroviruses as well as RNA in boiled human stool samples, with a sensitivity of 50 norovirus genome copies per reaction. The whole detection procedure of the one-step RT-RPA-LF is completed within 20 min, which is eight times faster than that of the standard real-time RT-PCR. The RT-RPA-LF method described here is suitable for rapid field diagnosis of all GII noroviruses in human stool samples.

Identification of a norovirus outbreak on a hematopoietic stem cell transplant unit and development and implementation of a novel infection prevention algorithm for controlling transmission

Controlling norovirus transmission in units with immunocompromised patients is challenging. We present a cluster of norovirus cases that occurred on a stem-cell transplant unit and the prevention efforts that were implemented to limit the outbreak. Protocols developed to control this cluster may provide a model for other facilities.

How Cities Cope in Outbreak Events?

An outbreak can cause more problems than just the spread of disease. It can be an antagonistic nemesis to our cities and communities, particularly if we lack preparedness and resilience. Its progress is usually unclear as it can be completely different from case to case, and can react differently in different contexts and with different groups of people. Such reactions may purely relate to climatic conditions, hygienic status, and environmental attributes of the context. Those reactions can also differ from one group of people to another, while the disease has to find its correct host as well the way it can transmit and evolve. Consequently, the magnitude of impacts would depend on many factors, of which the nature of the disease is very important during the whole outbreak progress.

Increased infection severity in downstream cities in infectious disease transmission and tourists surveillance analysis

Infectious disease severely threatens human life. Human mobility and travel patterns influence the spread of infection between cities and countries. We find that the infection severity in downstream cities during outbreaks is related to transmission rate, recovery rate, travel rate, travel duration and the average number of person-to-person contacts per day. The peak value of the infected population in downstream cities is slightly higher than that in source cities. However, as the number of cities increases, the severity increase percentage during outbreaks between end and source cities is constant. The surveillance of important nodes connecting cities, such as airports and train stations, can help delay the occurrence time of infection outbreaks. The city-entry surveillance of hub cities is not only useful to these cities, but also to cities that are strongly connected (i.e., have a high travel rate) to them. The city-exit surveillance of hub cities contributes to other downstream cities, but only slightly to itself. Surveillance conducted in hub cities is highly efficient in controlling infection transmission. Only strengthening the individual immunity of frequent travellers is not efficient for infection control. However, reducing the number of person-to-person contacts per day effectively limits the spread of infection.

Quantifying the relative effects of environmental and direct transmission of norovirus

Norovirus is a common cause of outbreaks of acute gastroenteritis in health- and child-care settings, with serial outbreaks also frequently observed aboard cruise ships. The relative contributions of environmental and direct person-to-person transmission of norovirus have hitherto not been quantified. We employ a novel mathematical model of norovirus transmission, and fit the model to daily incidence data from a major norovirus outbreak on a cruise ship, and examine the relative efficacy of potential control strategies aimed at reducing environmental and/or direct transmission. The reproduction number for environmental and direct transmission combined is [Formula: see text] [6.1,9.5], and of environmental transmission alone is [Formula: see text] [0.9,2.6]. Direct transmission is overwhelmingly due to passenger-to-passenger contacts, but crew can act as a reservoir of infection from cruise to cruise. This is the first quantification of the relative roles of environmental and direct transmission of norovirus. While environmental transmission has the potential to maintain a sustained series of outbreaks aboard a cruise ship in the absence of strict sanitation practices, direct transmission dominates. We find that intensive promotion of good hand washing practices may prevent outbreaks. Isolation of ill passengers and cleaning are beneficial, but appear to be less efficacious at outbreak control.

Norovirus and Clostridium difficile outbreaks: squelching the wildfire

PURPOSE OF REVIEW

Gastrointestinal outbreaks in the healthcare setting cause increased morbidity and mortality in an already vulnerable population. Optimization of infection prevention measures can be a challenge in healthcare settings. This review describes new literature that may change the traditional infection prevention approach to such outbreaks.

RECENT FINDINGS

Asymptomatic carriers of both norovirus and Clostridium difficile can pose risk of transmission to others and the environment. Rapid recognition and diagnosis can decrease the extent of an outbreak. No-touch technologies for environmental disinfection are new and effective tools. Infection prevention consultant services and systems redesign can augment efforts to control baseline infection rates and outbreaks. Antimicrobial stewardship continues to be essential to prevent C. difficile infection.

SUMMARY

New approaches are needed to stem the tide of norovirus and C. difficile clusters and outbreaks in healthcare settings. Accurate recognition, testing, and implementation of infection prevention measures can be supported with rapid testing modalities, access to updated guidelines and no-touch disinfection systems. The work-environment culture should be carefully assessed and restructured using human engineering models to promote effective infection prevention practices. Antimicrobial stewardship initiatives are needed at the bedside and at national levels.

Recombinase polymerase amplification: a promising point-of-care detection method for enteric viruses

Viral enteric disease imposes a considerable public health and economic burden globally in both humans and livestock. Because enteric viruses are highly transmissible and resistant to numerous control strategies, making early in-field or point-of-care detection is important. There are problems with ligand-based detection strategies (e.g., sensitivity, false positive/negatives) for virus detection. Traditional amplification-based strategies are sensitive, but not as portable or rapid. Recombinase polymerase amplification is a new isothermal technique that utilizes bacterial genome repair enzymes to rapidly amplify target sequences. This report reviews the use of recombinase polymerase amplification for virus detection, showing that the method has favorable fundamental properties supporting its promise for rapid point-of-care detection of enteric viruses.

Role of phosphate groups on antiviral activity of casein phosphopeptide against feline calicivirus as a surrogate for norovirus

BACKGROUND

Current research on the gastrointestinal digestion of milk-casein strongly suggests the existence of novel bioactive peptides with antiviral activities that are attributable to their immunostimulatory effects. In the present study, we investigated the antiviral activity of casein peptides rich in phosphate groups, such as casein phosphopeptide (CPP-III).

RESULTS

We prepared two types of CPP with different phosphorylation levels to clarify the role of the phosphate group. Further phosphorylation of CPP-III was conducted by dry heating with sodium pyrophosphate, whereas dephosphorylation was performed enzymatically using alkaline phosphatase and alkaline treatment. Feline calicivirus (FCV) strain F9, a typical norovirus surrogate, and Crandell Rees feline kidney cells were used as the target virus and host cells, respectively. Antiviral activity was determined based on the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and quantitative polymerase chain reaction quantification of antiviral cytokine mRNA expression. Higher cell viability was observed in the host cells treated with phosphorylated CPP-III, and a significant up-regulation of type 1 interferon expression was induced compared to that treated with native CPP-III. However, dephosphorylation of CPP-III resulted in a decrease in the anti-FCV effect.

CONCLUSION

The CPP effect was enhanced by the introduction of additional phosphates and conversely weakened by their elimination. Therefore, CPP-III phosphorylation represents an emerging approach for the production of food-grade antiviral agents. © 2016 Society of Chemical Industry.

Development of a Recombinase Polymerase Amplification Assay for Detection of Epidemic Human Noroviruses

Human norovirus is a leading cause of viral gastroenteritis worldwide. Rapid detection could facilitate control, however widespread point-of-care testing is infrequently done due to the lack of robust and portable methods. Recombinase polymerase amplification (RPA) is a novel isothermal method which rapidly amplifies and detects nucleic acids using a simple device in near real-time. An RT-RPA assay targeting a recent epidemic human norovirus strain (GII.4 New Orleans) was developed and evaluated in this study. The assay successfully detected purified norovirus RNA from multiple patient outbreak isolates and had a limit of detection of 3.40 ± 0.20 log₁₀ genomic copies (LGC), which is comparable to most other reported isothermal norovirus amplification methods. The assay also detected norovirus in directly boiled stool, and displayed better resistance to inhibitors than a commonly used RT-qPCR assay. The assay was specific, as it did not amplify genomes from 9 non-related enteric viruses and bacteria. The assay detected norovirus in some samples in as little as 6 min, and the entire detection process can be performed in less than 30 min. The reported RT-RPA method shows promise for sensitive point-of-care detection of epidemic human norovirus, and is the fastest human norovirus amplification method to date.

Potential economic burden of carbapenem-resistant Enterobacteriaceae (CRE) in the United States

OBJECTIVES

The Centers for Disease Control and Prevention considers carbapenem-resistant Enterobacteriaceae (CRE) an urgent public health threat; however, its economic burden is unknown.

METHODS

We developed a CRE clinical and economics outcomes model to determine the cost of CRE infection from the hospital, third-party payer, and societal, perspectives and to evaluate the health and economic burden of CRE to the USA.

RESULTS

Depending on the infection type, the median cost of a single CRE infection can range from $22 484 to $66 031 for hospitals, $10 440 to $31 621 for third-party payers, and $37 778 to $83 512 for society. An infection incidence of 2.93 per 100 000 population in the USA (9418 infections) would cost hospitals $275 million (95% CR $217-334 million), third-party payers $147 million (95% CR $129-172 million), and society $553 million (95% CR $303-1593 million) with a 25% attributable mortality, and would result in the loss of 8841 (95% CR 5805-12 420) quality-adjusted life years. An incidence of 15 per 100 000 (48 213 infections) would cost hospitals $1.4 billion (95% CR $1.1-1.7 billion), third-party payers $0.8 billion (95% CR $0.6-0.8 billion), and society $2.8 billion (95% CR $1.6-8.2 billion), and result in the loss of 45 261 quality-adjusted life years.

CONCLUSIONS

The cost of CRE is higher than the annual cost of many chronic diseases and of many acute diseases. Costs rise proportionally with the incidence of CRE, increasing by 2.0 times, 3.4 times, and 5.1 times for incidence rates of 6, 10, and 15 per 100 000 persons.

Evidence-Based interventions of Norovirus outbreaks in China

Background

In resource-limited settings where laboratory capacity is limited and response strategy is non-specific, delayed or inappropriate intervention against outbreaks of Norovirus (NoV) are common. Here we report interventions of two norovirus outbreaks, which highlight the importance of evidence-based modeling and assessment to identify infection sources and formulate effective response strategies.

Methods

Spatiotemporal scanning, mathematical and random walk modeling predicted the modes of transmission in the two incidents, which were supported by laboratory results and intervention outcomes.

Results

Simulation results indicated that contaminated water was 14 to 500 fold more infectious than infected individuals. Asymptomatic individuals were not effective transmitters. School closure for up to a week still could not contain the outbreak unless the duration was extended to 10 or more days. The total attack rates (TARs) for waterborne NoV outbreaks reported in China (n = 3, median = 4.37) were significantly (p < 0.05) lower than worldwide (n = 14, median = 41.34). The low TARs are likely due to the high number of the affected population.

Conclusions

We found that school closure alone could not contain Norovirus outbreaks. Overlooked personal hygiene may serve as a hotbed for infectious disease transmission. Our results reveal that evidence-based investigations can facilitate timely interventions of Norovirus transmission.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3716-3) contains supplementary material, which is available to authorized users.

Ionizing air affects influenza virus infectivity and prevents airborne-transmission

By the use of a modified ionizer device we describe effective prevention of airborne transmitted influenza A (strain Panama 99) virus infection between animals and inactivation of virus (>97%). Active ionizer prevented 100% (4/4) of guinea pigs from infection. Moreover, the device effectively captured airborne transmitted calicivirus, rotavirus and influenza virus, with recovery rates up to 21% after 40 min in a 19 m³ room. The ionizer generates negative ions, rendering airborne particles/aerosol droplets negatively charged and electrostatically attracts them to a positively charged collector plate. Trapped viruses are then identified by reverse transcription quantitative real-time PCR. The device enables unique possibilities for rapid and simple removal of virus from air and offers possibilities to simultaneously identify and prevent airborne transmission of viruses.

Norovirus Genotypes in Hospital Settings: Differences Between Nosocomial and Community-Acquired Infections

BACKGROUND

Norovirus (NoV) is a major cause of gastroenteritis and hospital outbreaks, leading to substantial morbidity and direct healthcare expenses as well as indirect societal costs. The aim of the study was to estimate the proportion of nosocomial NoV infections among inpatients testing positive for NoV in Denmark, 2002-2010, and to study the distribution of NoV genotypes among inpatients with nosocomial and community-acquired NoV infections, respectively.

METHODS

Admission and stool sampling dates from 3656 NoV-infected patients were used to estimate the proportion of nosocomial infections. The associations between nosocomial infection and patient age, sex, and NoV genotype GII.4 were examined.

RESULTS

Of the 3656 inpatients, 63% were classified as having nosocomial infections. Among these, 9 capsid and 8 polymerase NoV genotypes were detected, whereas in the smaller group of inpatients with community-acquired infections, 12 capsid and 9 polymerase genotypes were detected. Nosocomial NoV infections were associated with age ≥60 years and infections with genotype GII.4.

CONCLUSIONS

The majority of NoV infections in hospitalized patients were nosocomial. Nosocomial infection was mainly associated with older age but also with the specific genotype GII.4. The genotypes in community-acquired NoV infections were more heterogeneous than in nosocomial infections.

Multiplex gastrointestinal pathogen panels: implications for infection control

In the acute care hospital inpatient setting, there is a wide variety of causes for both infectious and noninfectious diarrhea. However, without molecular assays for the wide range of agents causing gastroenteritis, there is no reliable way to determine which individuals should be placed in contact precautions, as recommended by CDC. We tested 158 inpatient diarrheal stool specimens with the FilmArray GI Panel (BioFire Diagnostics, Salt Lake City, UT, USA) that had been stored at -70°C after testing negative by conventional methods for Clostridium difficile and/or rotavirus. We found that 22.2% had at least 1 other infectious agent detected, and 60% of these patients were never placed in appropriate isolation for a total of 109 patient-days. In addition, 20.3% of patients with negative GI panel results could have been removed from isolation. Use of multiplex gastrointestinal panels may improve decisions regarding patient isolation and reduce nosocomial transmission.

Infection control for norovirus

Norovirus infections are notoriously difficult to prevent and control, owing to their low infectious dose, high shedding titre, and environmental stability. The virus can spread through multiple transmission routes, of which person-to-person and foodborne are the most important. Recent advances in molecular diagnostics have helped to establish norovirus as the most common cause of sporadic gastroenteritis and the most common cause of outbreaks of acute gastroenteritis across all ages. In this article, we review the epidemiology and virology of noroviruses, and prevention and control guidelines, with a focus on the principles of disinfection and decontamination. Outbreak management relies on sound infection control principles, including hand hygiene, limiting exposure to infectious individuals, and thorough environmental decontamination. Ideally, all infection control recommendations would rely on empirical evidence, but a number of challenges, including the inability to culture noroviruses in the laboratory and the challenges of outbreak management in complex environments, has made it difficult to garner clear evidence of efficacy in certain areas of infection control. New experimental data on cultivable surrogates for human norovirus and on environmental survivability and relative resistance to commonly used disinfectants are providing new insights for further refinining disinfection practices. Finally, clinical trials are underway to evaluate the efficacy of vaccines, which may shift the current infection control principles to more targeted interventions.

Infection control for norovirus

Norovirus infections are notoriously difficult to prevent and control, owing to their low infectious dose, high shedding titre, and environmental stability. The virus can spread through multiple transmission routes, of which person-to-person and foodborne are the most important. Recent advances in molecular diagnostics have helped to establish norovirus as the most common cause of sporadic gastroenteritis and the most common cause of outbreaks of acute gastroenteritis across all ages. In this article, we review the epidemiology and virology of noroviruses, and prevention and control guidelines, with a focus on the principles of disinfection and decontamination. Outbreak management relies on sound infection control principles, including hand hygiene, limiting exposure to infectious individuals, and thorough environmental decontamination. Ideally, all infection control recommendations would rely on empirical evidence, but a number of challenges, including the inability to culture noroviruses in the laboratory and the challenges of outbreak management in complex environments, has made it difficult to garner clear evidence of efficacy in certain areas of infection control. New experimental data on cultivable surrogates for human norovirus and on environmental survivability and relative resistance to commonly used disinfectants are providing new insights for further refinining disinfection practices. Finally, clinical trials are underway to evaluate the efficacy of vaccines, which may shift the current infection control principles to more targeted interventions.

Detecting the norovirus season in Sweden using search engine data--meeting the needs of hospital infection control teams

Norovirus outbreaks severely disrupt healthcare systems. We evaluated whether Websök, an internet-based surveillance system using search engine data, improved norovirus surveillance and response in Sweden. We compared Websök users' characteristics with the general population, cross-correlated weekly Websök searches with laboratory notifications between 2006 and 2013, compared the time Websök and laboratory data crossed the epidemic threshold and surveyed infection control teams about their perception and use of Websök. Users of Websök were not representative of the general population. Websök correlated with laboratory data (b = 0.88-0.89) and gave an earlier signal to the onset of the norovirus season compared with laboratory-based surveillance. 17/21 (81%) infection control teams answered the survey, of which 11 (65%) believed Websök could help with infection control plans. Websök is a low-resource, easily replicable system that detects the norovirus season as reliably as laboratory data, but earlier. Using Websök in routine surveillance can help infection control teams prepare for the yearly norovirus season.

Economics and financing of vaccines for diarrheal diseases

The considerable burden of infectious disease-caused diarrhea around the world has motivated the continuing development of a number of vaccine candidates over the past several decades with some reaching the market. As with all major public health interventions, understanding the economics and financing of vaccines against diarrheal diseases is essential to their development and implementation. This review focuses on each of the major infectious pathogens that commonly cause diarrhea, the current understanding of their economic burden, the status of vaccine development, and existing economic evaluations of the vaccines. While the literature on the economics and financing of vaccines against diarrhea diseases is growing, there is considerable room for more inquiry. Substantial gaps exist for many pathogens, circumstances, and effects. Economics and financing studies are integral to vaccine development and implementation.

Expert Recommendations for Managing Acute Faecal Incontinence with Diarrhoea in the Intensive Care Unit

Acute faecal incontinence with diarrhoea (AFId) has been reported to affect up to 40% of patients in the intensive care unit (ICU). The clinical challenges of AFId include the risk of perineal skin breakdown and cross-contamination with nosocomial infections, such as Clostridium difficile. In addition, the management of AFId is a burden on nursing time and hospital resources. Despite these challenges, there is currently no standard way of managing AFId. To address this problem, an international panel of intensive care specialists was convened to discuss AFId management recommendations. The collective knowledge of the specialists combined with literature searches from online medical databases were used to create a set of guidelines together with an accompanying management algorithm to aid healthcare providers in deciding the most appropriate care for patients with AFId in the ICU. These guidelines have been specifically designed to take into account patient severity of illness and comorbidities, which coupled with common AFId-associated clinical complications, can influence management choices. A comprehensive review of current AFId management strategies, taking into account the spectrum of patients and hospital economic limitations, has been included as a reference guide. It is hoped that the wider adoption of these recommendations will be a step forward in improving the current management of AFId in the ICU.

Prevention of influenza in healthy children

Healthy children are high transmitters of influenza and can experience poor influenza outcomes. Many questions remain about the efficacy and impect of preventive measures because most existing studies report imprecise proxies of influenza incidence, do not follow subjects throughout the entire influenza season and across multiple influenza seasons, or do not control for important factors such as timing of implementation and social contact patterns. Modeling and simulation are key methodologies to answer questions regarding influenza prevention. While vaccination may be the most efficacious existing intervention, variations in circulating strains and children's immune systems keep current vaccines from being fully protective, necessitating further clinical and economic studies and technology improvements. Hand hygiene appears to be an important adjunct but improving compliance, standardizing regimens and quantifying its impact remain challenging. Future studies should help better define the specific indications and circumstances for antiviral use and the role of nutritional supplements and nonpharmaceutical interventions.

Evidence that contaminated surfaces contribute to the transmission of hospital pathogens and an overview of strategies to address contaminated surfaces in hospital settings

Evidence that contaminated surfaces contribute to the transmission of hospital pathogens comes from studies modeling transmission routes, microbiologic studies, observational epidemiologic studies, intervention studies, and outbreak reports. This review presents evidence that contaminated surfaces contribute to transmission and discusses the various strategies currently available to address environmental contamination in hospitals.

Impact of introducing the pneumococcal and rotavirus vaccines into the routine immunization program in Niger

OBJECTIVES

We investigated whether introducing the rotavirus and pneumococcal vaccines, which are greatly needed in West Africa, would overwhelm existing supply chains (i.e., the series of steps required to get a vaccine from the manufacturers to the target population) in Niger.

METHODS

As part of the Bill and Melinda Gates Foundation-funded Vaccine Modeling Initiative, we developed a computational model to determine the impact of introducing these new vaccines to Niger's Expanded Program on Immunization vaccine supply chain.

RESULTS

Introducing either the rotavirus vaccine or the 7-valent pneumococcal conjugate vaccine could overwhelm available storage and transport refrigerator space, creating bottlenecks that would prevent the flow of vaccines down to the clinics. As a result, the availability of all World Health Organization Expanded Program on Immunization vaccines to patients might decrease from an average of 69% to 28.2% (range = 10%-51%). Addition of refrigerator and transport capacity could alleviate this bottleneck.

CONCLUSIONS

Our results suggest that the effects on the vaccine supply chain should be considered when introducing a new vaccine and that computational models can help assess evolving needs and prevent problems with vaccine delivery.

Genetic mapping of a highly variable norovirus GII.4 blockade epitope: potential role in escape from human herd immunity

Noroviruses account for 96% of viral gastroenteritis cases worldwide, with GII.4 strains responsible >80% of norovirus outbreaks. Histo-blood group antigens (HBGAs) are norovirus binding ligands, and antigenic and preferential HBGA binding profiles vary over time as new GII.4 strains emerge. The capsid P2 subdomain facilitates HBGA binding, contains neutralizing antibody epitopes, and likely evolves in response to herd immunity. To identify amino acids regulating HBGA binding and antigenic differences over time, we created chimeric virus-like particles (VLPs) between the GII.4-1987 and GII.4-2006 strains by exchanging amino acids in putative epitopes and characterized their antigenic and HBGA binding profiles using anti-GII.4-1987 and -2006 mouse monoclonal antibodies (MAbs) and polyclonal sera, 1988 outbreak human sera, and synthetic HBGAs. The exchange of amino acids 393 to 395 between GII.4-1987 and GII.4-2006 resulted in altered synthetic HBGA binding compared to parental strains. Introduction of GII.4-1987 residues 294, 297 to 298, 368, and 372 (epitope A) into GII.4-2006 resulted in reactivity with three anti-GII.4-1987 MAbs and reduced reactivity with four anti-GII.4-2006 MAbs. The three anti-GII.4-1987 MAbs also blocked chimeric VLP-HBGA interaction, while an anti-GII.4-2006 blocking antibody did not, indicating that epitope A amino acids comprise a potential neutralizing epitope for GII.4-1987 and GII.4-2006. We also tested GII.4-1987-immunized mouse polyclonal sera and 1988 outbreak human sera for the ability to block chimeric VLP-HBGA interaction and found that epitope A amino acids contribute significantly to the GII.4-1987 blockade response. Our data provide insights that help explain the emergence of new GII.4 epidemic strains over time, may aid development of norovirus therapeutics, and may help predict the emergence of future epidemic strains.

The economic burden of Clostridium difficile

Although Clostridium difficile (C. difficile) is the leading cause of infectious diarrhoea in hospitalized patients, the economic burden of this major nosocomial pathogen for hospitals, third-party payers and society remains unclear. We developed an economic computer simulation model to determine the costs attributable to healthcare-acquired C. difficile infection (CDI) from the hospital, third-party payer and societal perspectives. Sensitivity analyses explored the effects of varying the cost of hospitalization, C. difficile-attributable length of stay, and the probability of initial and secondary recurrences. The median cost of a case ranged from $9179 to $11 456 from the hospital perspective, $8932 to $11 679 from the third-party payor perspective, and $13 310 to $16 464 from the societal perspective. Most of the costs incurred were accrued during a patient's primary CDI episode. Hospitals with an incidence of 4.1 CDI cases per 100 000 discharges would incur costs ≥$3.2 million (hospital perspective); an incidence of 10.5 would lead to costs ≥$30.6 million. Our model suggests that the annual US economic burden of CDI would be ≥$496 million (hospital perspective), ≥$547 million (third-party payer perspective) and ≥$796 million (societal perspective). Our results show that C. difficile infection is indeed costly, not only to third-party payers and the hospital, but to society as well. These results are consistent with current literature citing C. difficile as a costly disease.

Human norovirus infection: surveillance and source tracking

The clinical importance of noroviruses has increased in recent years. It is challenging to control the annual gastroenteritis and vomiting outbreaks caused by noroviruses in hospital wards and also long-term care facilities. This problem is partly due to the repeated emergence of highly penetrant genotype GII.4 variants that cause global epidemics. Consequently, this has led to an increased awareness of norovirus receptor selection and the population immunity characteristics that drive the evolution of the virus. Noroviruses mainly transmit from person to person by the feco–oral route and also via food, water and environmental fomites. International norovirus surveillance helps in source-tracking and in being able to follow the dissemination of viruses with food products in addition to the early detection of emerging variants.