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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

Human noroviruses: Challenges in Prevention and Control

Dr. Kristen Gibson

Assistant Professor, Department of Food Science

University of Arkansas

AFDO Conference

some history
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
common misnomers for norovirus
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
virus structure and function
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.
foodborne viruses of human health concern are
Foodborne viruses of human health concern are:
  • Non-enveloped
  • Small (25-100 nm)
  • Resistant to environmental degradation
norovirus
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

slide20
80%

Glass et al., 2009

norovirus1
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

norovirus2
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

u s foodborne outbreaks 2009 2010
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

food safety issue
Food safety issue?
  • Highly contagious
  • Prolific shedding
  • Constantly evolving
  • Limited immunity
  • Moderately virulent

Large pool of

susceptible hosts

food safety issue1
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.

food as a vehicle for norovirus transmission
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.
food as a vehicle for norovirus transmission1
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
critical control points
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
cleaning cloths
Cleaning Cloths?

Cellulose Cotton

Cellulose Cotton

Microfiber

Nonwoven Cloth

Cotton Terry Towel

primary questions
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?
cleaning cloth study1
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
cleaning cloth study2
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
cleaning cloth study virus transfer
Cleaning Cloth Study: Virus Transfer

Two log difference in virus transfer between cellulose/cotton

and terry towel cloths.

cleaning cloth study3
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?
slide41
Outbreaks associated with food or restaurant settings have significantly

higher attack rates (>50%) than outbreaks in other settings.

how to address food safety and norovirus
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
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