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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 2982 samples, 2038 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, 2038 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.

Aims\ud This study evaluated detection methods for Salmonella Typhi (S. Typhi) in the environment, to establish a novel pathway from field sampling to isolation of viable organisms and molecular confirmation from complex environmental samples, thus enabling environmental surveillance of typhoid.\ud \ud Methods and Results\ud Multiple media were assessed using clinical isolates from the Public Health England’s (PHE) Culture collection. The culture pathway selected consisted of a primary 2% bile broth and secondary Selenite F broth, followed by modified Chromogenic Agar for Salmonella Esterase (mCASE). A qPCR assay was adapted from a validated S. Typhi PCR panel for confirmation of isolates, with comparison to biochemical and serological tests showing good specificity. Sampling locations in Blantyre, Malawi were used to compare sampling methods. Viable S. Typhi were isolated from a mixture of trap and grab river water samples on six occasions.\ud \ud Conclusions\ud Culture of viable S. Typhi from environmental samples was possible using effective capture and culture techniques.\ud Significance and impact of study\ud \ud Whilst several studies have attempted to detect S. Typhi from the environment, this is the first successful attempt to isolate the organism from river water since the 1980’s. Supplementing clinical data with environmental screening offers the potential for enhanced surveillance, which might inform interventions and assess vaccination programmes.

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