The development of viral capture, concentration and molecular detection method for norovirus in foods to establish the risk to public health

Norovirus has been identified as a common cause of gastroenteritis worldwide, and food as a transmission vehicle has been well documented. Standardised detection methods exist for the detection of norovirus from fresh produce and molluscan bivalves, whilst detection methods for a wider range of food matrices that may be implicated in transmission of norovirus do not currently exist. The detection of norovirus in foods suspected to be implicated in transmission is paramount for appropriate outbreak investigation. The contamination of foods other than shellfish and fresh produce often occurs via food handlers. The proportion of norovirus that is typically transferred from food handlers to food also remains unknown. Understanding this is necessary in order to estimate the risk of infection and the burden of gastroenteritis caused by norovirus that is attributable to food contaminated by food handlers. These questions were addressed by the development of a combined capture, concentration and quantitative detection protocol with the aim to enhanced norovirus recovery from a range of food types. A food surface wash and norovirus capture method that was sensitive, reduced processing time, and increased throughput capacity was applied to a range of ready to eat foods. An automated nucleic acid extraction method which further reduced processing time and increased throughput was validated. Finally the validated method demonstrated that two real time RT-PCR assays currently used for the detection of norovirus in shellfish and fresh produce or in faecal samples were comparable overall, and hence either could be used in combination with the norovirus capture, concentration and extraction protocol described in this thesis. The protocol was applied to a range of food matrices and resulted in <1% to 55% recovery of norovirus GI and <1% to 25% recovery of norovirus GII. The optimised protocol was then used to quantify virus transfer between food handlers hands and to food, in simulation experiments where food handlers’ gloved hands were artificially contaminated prior to preparation of a sandwich. This enabled norovirus transfer to food items and to other food handlers to be measured at each stage. Quantitative data demonstrated that 5.9 ± (SD ± 0.1) log10 cDNA copies/µl of norovirus GII inoculum, resulted in a percentage recovery of between 3.0% and 0.02% from Food Handlers and 7.8 ± (SD ± 0.1) log10 cDNA copies/µl of norovirus GI inoculum resulted in a percentage recovery between 9.6% and 0.004% from Food Handlers. The average percentage recovered from sandwich pieces over six replicates was 0.2% for norovirus GII and 1.2% for norovirus GI. The method and protocols developed could be rolled out to official control laboratories and aid foodborne outbreak investigation by allowing testing of food categories that currently are not investigated. Furthermore, this work demonstrated the extent of norovirus transfer from hands to food ingredients and the environment and could be used in risk assessment models. Further work applying these protocols to quantify the transfer from contaminated hands using a range of viral loads will be useful in determining risk more accurately, and to monitor and investigate food premises by introducing this as an additional food and hand hygiene marker

Imaging Spectrometer Implementation on a Small Satellite Platform for Aquatic Ecosystems Science

The implementation of Imaging spectrometers with state-of-the-art performance on small satellites is challenging due to the size, weight, and power (SWaP) limitations. We have recently developed a compact form, the Chrisp Compact VNIR/SWIR Imaging Spectrometer (CCVIS), that facilitates their usage without sacrificing performance. The CCVIS enables a modular implementation that, combined with a freeform telescope, produces a wide field of view with high signal to noise ratio (SNR) performance. The targeted scientific application is the study of aquatic ecosystems. The imaging spectrometer is designed to address carbon sequestration in coastal margins and wetlands, kelp and seagrass studies, coral reefs, harmful algal blooms and hypoxia, and carbon cycling in this dynamic environment. The requirements are challenging since the high SNR, which is necessary in order to produce quality data products over water, is coupled with sufficient dynamic range in order to simultaneously record spectra from the shore area, which has elevated spectral radiance in comparison to the water. To meet these requirements, the small satellite will execute a pitchback maneuver where the imaging of the slit projected onto the surface is slowly scanned while recording focal plane array (FPA) readouts at a higher rate. The effective frame rate is determined by the time it takes to scan the projected slit one ground sample distance (GSD). This concept of operation avoids saturation over the land surface while obtaining high SNR over the water. This approach has the added benefit of measuring a range of angles during a single GSD acquisition, providing insight into the bidirectional reflectance distribution function (BRDF). One consequence of this approach is extremely large data volumes requiring a high bandwidth downlink system. Laser communications is a critical technology that enables the transfer of these large data volumes. We present a preliminary design of the imaging spectrometer based on the aquatic ecosystem requirements including the modular implementation of the CCVIS, the laser communications system, and the implementation on a ESPA-grande satellite

Measuring transfer of human norovirus during sandwich production: Simulating the role of food, food handlers and the environment.

Foodborne outbreaks associated with transmission of norovirus are increasingly becoming a public health concern. Foods can be contaminated with faecal material at the point of production or during food preparation, in both the home and in commercial premises. Transmission of norovirus occurs through the faecal-oral route, either via person-to-person contact or through faecal-contamination of food, water, or environmental surfaces. Understanding the role and pathways of norovirus transmission - either via food handlers' hands, contaminated foods or the environment - remains a key public health priority to reduce the burden of norovirus-associated gastroenteritis. However the proportion of norovirus that is typically transferred remains unknown. Understanding this is necessary to estimate the risk of infection and the burden of gastroenteritis caused by norovirus. In this paper we present a novel method of capture, concentration and molecular detection of norovirus from a wider range of complex food matrices than those demonstrated in existing published methods. We demonstrate that this method can be used as a tool to detect and quantify norovirus from naturally contaminated food, and for monitoring norovirus transfer between food handlers' gloved hands, food or the environment. We measure the effect of introducing contamination at different food production process stages, to the final food product, to determine whether this could cause infection and disease. Between 5.9 and 6.3 Log10 cDNA copies/?l of norovirus GII were inoculated onto food handlers' gloved hands, food or the environment and 1.1-7.4% of norovirus contamination was recovered from all samples tested. When interpreted quantitatively, this percentage equates to levels predicted to be sufficient to cause infection and disease through consumption of the final food product, demonstrating a public health risk. Overall detection and quantification of norovirus from foods, food handlers' gloved hands and the environment, when suspected to be implicated in foodborne transmissions, is paramount for appropriate outbreak investigation

Deep Inelastic Scattering at HERA

Results from the H1 and ZEUS experiments at HERA on deep inelastic scattering are reviewed. The data lead to a consistent picture of a steep rise in the F_2 structure function and in the gluon density within the proton. Important new information on the partonic structure of diffraction is emerging from H1 and ZEUS. The space-like region in which the weak and electromagnetic interactions become of equal strength is being explored for the first time. A possible excess of events at high x and Q^2 compared to the expectations of the Standard Model has been observed in both experiments.Comment: 80 pages, 42 figure

Resolved Photon Processes

We review the present level of knowledge of the hadronic structure of the photon, as revealed in interactions involving quarks and gluons ``in" the photon. The concept of photon structure functions is introduced in the description of deep--inelastic $e \gamma$ scattering, and existing parametrizations of the parton densities in the photon are reviewed. We then turn to hard \gamp\ and \gaga\ collisions, where we treat the production of jets, heavy quarks, hard (direct) photons, \jpsi\ mesons, and lepton pairs. We also comment on issues that go beyond perturbation theory, including recent attempts at a comprehensive description of both hard and soft \gamp\ and \gaga\ interactions. We conclude with a list of open problems.Comment: LaTeX with equation.sty, 85 pages, 29 figures (not included). A complete PS file of the paper, including figures, can be obtained via anonymous ftp from ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-898.ps.

COVID-19 herd immunity in the absence of a vaccine : an irresponsible approach

As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread rapidly throughout the human population, the concept of "herd immunity" has attracted the attention of both decision-makers and the general public. In the absence of a vaccine, this entails that a large proportion of the population will be infected to develop immunity that would limit the severity and/or extent of subsequent outbreaks. We argue that adopting such an approach should be avoided for several reasons. There are significant uncertainties about whether achieving herd immunity is possible. If possible, achieving herd immunity would impose a large burden on society. There are gaps in protection, making it difficult to shield the vulnerable. It would defeat the purpose of avoiding harm caused by the virus. Lastly, dozens of countries are showing that containment is possible

Norovirus Attribution Study: Detection of norovirus from the commercial food preparation environment in outbreak and non-outbreak premises.

AIMS: Norovirus remains the most significant virological risk that is transmitted via food and the environment to cause acute gastroenteritis. This study aimed to investigate the hypothesis that the contamination of the commercial food production environment with norovirus will be higher in premises that have recently reported a foodborne norovirus outbreak than those that have not. METHODS: Sampling of commercial food production environments was carried out across a 16-month period between January 2015 and April 2016 in the South East and the North West of England by local authority environmental health departments as part of routine surveillance visits to premises. A total of 2,982 samples, 2,038 virological and 944 bacteriological, were collected from 256 premises. Sixteen of these premises, six from South East and ten from North West England, were sampled as part of a public health outbreak investigation. RESULTS & CONCLUSIONS: Overall, 2,038 swabs were submitted for norovirus testing, with an average of eight swabs per premises (range 4 to 23) and a median of seven. Of the premises sampled, 11.7 % (30/256) yielded at least one norovirus positive sample (environmental, and/or food handler hand swab), and 2.5 % of the swabs were positive for norovirus. A peak in the positivity rate was seen in the South East in April 2016. No associations were found between norovirus positivity and bacteriology indicators, or between bacteriology indicators and hygiene ratings. SIGNIFICANCE AND IMPACT OF STUDY: This study demonstrates that food premises and food handlers remain a potential source of norovirus transmission and outbreaks