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Human noroviruses : Challenges in Prevention and Control

Human noroviruses : Challenges in Prevention and Control. Dr. Kristen Gibson Assistant Professor, Department of Food Science University of Arkansas AFDO Conference. Norovirus Transmission. Some history…. Discovered in 1972 by EM

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Human noroviruses : Challenges in Prevention and Control

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  1. Human noroviruses: Challenges in Prevention and Control Dr. Kristen Gibson Assistant Professor, Department of Food Science University of Arkansas AFDO Conference

  2. NorovirusTransmission

  3. Some history… • Discovered in 1972 by EM • Infectious stool filtrate derived from outbreak in an elementary school in Norwalk, OH (1968) • Originally called “Norwalk virus” • Prototype strain of the noroviruses

  4. Common Misnomers for Norovirus • Stomach Flu • “24-hour” Flu • Winter Vomiting Disease • Cruise Ship Virus • Norovirus is commonly • referred to as the “flu”: • seasonal component • rapid onset

  5. Over 90% of diarrheal illness outbreaks on cruise ships are due to norovirus.

  6. Norovirus: 2012-2013

  7. Virus Structure and Function • Viruses are small, intracellular parasites that cannot reproduce by themselves. • An infectious virus particle is referred to as a virion. • A virion consists of the nucleic acid and an outer shell of protein, referred to as a capsid. • A virion may be enveloped or non-enveloped. • Most viral host ranges are narrow.

  8. Foodborne viruses of human health concern are: • Non-enveloped • Small (25-100 nm) • Resistant to environmental degradation

  9. How small is “small”?

  10. How small is “small”?

  11. How small is “small”?

  12. How small is “small”?

  13. How small is “small”?

  14. How small is “small”?

  15. How small is “small”?

  16. How small is “small”?

  17. How small is “small”?

  18. How small is “small”?

  19. Norovirus • Single-stranded RNA, non-enveloped viruses • 5 genogroups (GI, GII, GIII, GIV, GV) and 31 genetic clusters • Human = GI, GII, and GIV CDC, 2006. Norovirus: Technical Fact Sheet; Hutsonet al. 2004

  20. 80% Glass et al., 2009

  21. Norovirus • Single-stranded RNA, non-enveloped viruses • 5 genogroups (GI, GII, GIII, GIV, GV) and 31 genetic clusters • Human = GI, GII, and GIV • Clinical Symptoms • 24-48 hr incubation • Vomiting, watery diarrhea, stomach cramps, nausea, and general malaise • Self-limiting (24-60 hrs) • No known chronic sequelae • Complications include volume depletion and dehydration • Potential for chronic infections in immunocompromised and physically stressed individuals CDC, 2006. Norovirus: Technical Fact Sheet; Hutsonet al. 2004

  22. Norovirus • Routes • Fecal-oral route (food, water, person-person) • Environmental and fomite contamination • Aerosolization of vomitus (hotel carpet, reusable grocery bags) • Ease of transmission • ID = 19 to 100 virions • High rate of secondary transmission • Immunity • Strain-specific, lasting only a few months • Population immunity plays role in formation of novel variants CDC, 2006. Norovirus:Technical Fact Sheet

  23. U.S. Foodborne Outbreaks 2009-2010 • Norovirus caused 49% (233) of lab confirmed single etiology outbreaks reported. • 34% due to an unknown etiology • Most common food commodity associated with NoV outbreaks are leafy vegetables. • NoV caused the most outbreaks from 1998 to 2008 Source: www.foodqualitynews.com www.cdc.gov

  24. Food safety issue? • Highly contagious • Prolific shedding • Constantly evolving • Limited immunity • Moderately virulent Large pool of susceptible hosts

  25. Food safety issue? • Persistence and Environmental Stability • Resistant to common chemical disinfectants • Thermo-tolerant • Survives for weeks on surfaces and for months in water Numerous NoV outbreaks each year are due to transmission via contaminated surfaces.

  26. Food as a Vehicle for Norovirus Transmission • Primary transmission • Contamination of foods in the “raw” material stage before harvest • Bivalve mollusks such as oysters • Application of contaminated water and sewage sludge to fruit and vegetable crops • Leafy vegetables, green onions, etc.

  27. Oysters and Norovirus

  28. Slide courtesy Michael T Osterholm University of Minnesota

  29. Slide courtesy Michael T Osterholm University of Minnesota

  30. Slide courtesy Michael T Osterholm University of Minnesota

  31. Food as a Vehicle for Norovirus Transmission • Primary transmission • Contamination of foods in the “raw” material stage before harvest • Bivalve mollusks such as oysters • Application of contaminated water and sewage sludge to fruit and vegetable crops • Leafy vegetables, green onions, etc. • Secondary transmission • Occurs during processing, storage, distribution, and final preparation • Field workers • Infected food handlers • Contaminated surfaces or equipment

  32. Retail Food Environments

  33. Critical Control Points • Hand hygiene • Hand sanitizers (NOT a replacement for…) • Hand washing • Appropriate sanitizers and disinfectants • Concentration • Contact time • Tools for application and cleaning • Spray, foam, impregnated wipes • Reusable or disposable cloths

  34. Cleaning Cloth Study

  35. Cleaning Cloths? Cellulose Cotton Cellulose Cotton Microfiber Nonwoven Cloth Cotton Terry Towel

  36. Primary Questions • What is the virus removal efficiency of each cloth? • Do the cloths transfer virus back to the surface? If so, what level of virus is transferred?

  37. Cleaning Cloth Study • Two surfaces • Stainless steel • Solid surface (e.g., formica) • 5 cleaning cloths • Cotton-cellulose blend (2) • Microfiber • Non-woven • Terry bar towel • 4 NoV surrogates and NoV GI.1

  38. Cleaning Cloth Study • Virus Removal • 100,000 to 1,000,000 viruses on surface • 700 viruses from solid surface across all cloths • 1,400 viruses from stainless steel across all cloths

  39. Cleaning Cloth Study: Virus Transfer Two log difference in virus transfer between cellulose/cotton and terry towel cloths.

  40. Cleaning Cloth Study • Use of appropriate cleaning tools is a CRITICAL step in controlling transmission • Reusable cloths may be reservoirs for transmission of pathogens • First study to look at virus removal and transfer by cleaning cloths…WHY?

  41. Outbreaks associated with food or restaurant settings have significantly higher attack rates (>50%) than outbreaks in other settings.

  42. How to Address Food Safety and Norovirus • Shift the approach used for monitoring and control strategies • Proactive vs. Reactive • Understand the characteristics of norovirus • Optimization of methods for the detection of norovirus in foodstuffs • Hazard Analysis and Critical Control Points (HACCP) • Better characterize risk posed by individual microbial contaminants • Investigate priority contaminants (i.e., norovirus) • Selection of appropriate treatment technology • Outbreak Surveillance • Passive vs. Active

  43. WASH YOUR HANDS

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