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Norovirus – A Case Study

Norovirus – A Case Study. 1 st Year PhD Student – Paul McMenemy(UoS) Primary Supervisor – Dr Adam Kleczkowski (UoS) Secondary Supervisor – Dr Frans de Vries (UoS) Industrial Supervisor – Dr Nick Taylor (CEFAS). News Headlines - Norovirus.

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Norovirus – A Case Study

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  1. Norovirus – A Case Study 1st Year PhD Student – Paul McMenemy(UoS) Primary Supervisor – Dr Adam Kleczkowski (UoS) Secondary Supervisor – Dr Frans de Vries (UoS) Industrial Supervisor – Dr Nick Taylor (CEFAS)

  2. News Headlines - Norovirus • “Cases of the winter vomiting bug 'top a million‘ “ – BBC , 28th Dec 2012 • “New strain of norovirus spreads around the world” – Yahoo News, 9th Jan 2013 • “New strain of norovirus” – Centre for Disease Control – USA, 14th Jan 2013 • “New Mutant Norovirus Strain to Wreak Havoc on Cruise Industry?” – cruiselawnews.com, 16th Jan 2013 • GII.4 Sydney strain – nicknamed “Down Ch-under” • Worldwide impact of new and existing virus strains • Becoming more prevalent in 21stcentury

  3. What is Norovirus? • Fever • Headache • Body aches (Sources – http://www.cdc.gov/norovirus/about/symptoms.html, http://www.cefas.defra.gov.uk ) • Small round structured virus (SRSV) • World’s main cause of gastroenteritis • Transmitted via the faecal-oral route • Eat/drink contaminated foodstuffs • Touch contaminated surfaces then put fingers in your mouth • Contact with someone who is infected • Many different strains of norovirus(NoV) • Person can be infected multiple times • Symptoms • Diarrhoea • Vomiting, Nausea • Stomach pain

  4. Norovirus in Shellfish Industry • Main cause - sewage • treatment works • Prevalent in most bivalves • Cooking shellfish kills NoV • Oysters eaten raw in U.K. Reduce NoV in oysters: Reduce NoV outbreaks

  5. U.K. Oyster Supply Chain Harvest Depuration Imports Wholesale Retail Initial focus of study Consumer

  6. Depuration Stage Oysters are flushed with clean water Reduces bacterial contaminants (E. coli) Limited impact on virus counts in oysters More straightforward to model than other stages Costly to depurate Can reduce oyster quality

  7. Probability Distribution Model – Depuration Stage • Use existing pre-depuration data (courtesy - james.lowther@cefas.co.uk) • Existing data split for genome types I and II • Find NoV count per oyster distribution function

  8. Probability Distribution Model – Depuration Stage Lognormal probability density function is: , Function to show relationship between and , ( – rate of change variable): As , we can generate a p.d.f. for from:

  9. Probability Density Function for norovirus count per oyster at time standard deviation of logged data mean of logged data rate at which norovirus counts per oyster changes number of time periods into depuration process

  10. plots for to

  11. Uses of Model Used to predict level of NoV present after time in depuration Used to determine optimal time in depuration to minimise NoV risk Allow cost-benefit analysis of depuration on NoV mitigation Could be also used for modelling E. coli

  12. Further Work • Model v ExperimentalData : • Data on NoV count before andafter depuration needed to validate and fine-tune model • Economic work on cost-benefit analysis • Create models on other stages of supply chain • Wholesale/Retail (storage, testing) • Consumer (awareness, frequency of consumption)

  13. Thank you for listening… Impact Collaborative Studentship funded by: The University of Stirling and Centre for Environment, Fisheries & Aquaculture Science

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