Noroviruses and Food borne Noroviruses and Food borne Disease:Disease:

A Little Pathogen that Causes Big A Little Pathogen that Causes Big ProblemsProblems

Lee-Ann Jaykus, Ph.D.Lee-Ann Jaykus, Ph.D.Professor and IAFP PresidentProfessor and IAFP President

What are the Human Enteric What are the Human Enteric Viruses?Viruses?

Obligate intracellular parasitesObligate intracellular parasites Simple structure, RNA genomeSimple structure, RNA genome Very smallVery small Transmitted by humansTransmitted by humans

• FecesFeces• Vomitus (Norovirus)Vomitus (Norovirus)

Highly transmissible Highly transmissible Difficult to:Difficult to:

• StudyStudy• DetectDetect

Duizer and Koopmans, 2007

Sources of Exposure to Enteric Viruses

Drinking Water FOODS Person-to-Person

“Direct” (f ecal) VI RUS TRANSMI SSI ON “I ndirect” (vomitus) Fomites Other Recreational waters Soil

At-Risk FoodsAt-Risk Foods

• Molluscan Shellfish• Fresh Produce • Ready-to-Eat Foods•Others

Grand Canyon Outbreak

Fig 1. Distribution of ill rafters by days from start of trip (N=137)

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Median norovirus incubation period (33 hours)

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Fig 2. Dates of launch for all rafting trips from implicated companies, and timeline of meat preparation and consumption, Grand Canyon,

Aug 14 - Sep 19, 2005

= Meat from “Batch 1” served on trip

Aug 13-14:

Meat-slicerill

Aug 15-16Batch 1

deli meat sliced

Aug 18-23:

Batch 1 delivered

Aug 19:

1st affected trip

Sep 12: Batch 1

withdrawn

Sep 15: Guide ill

Sep 17:Other rafters ill

Not served meat from Batch 1, but guide ate withdraqwn Batch 1 meat 1 day before embarking and likely seeded outbreak.on trip

Source: Malek et al., 2009

Food borne Enteric Viruses of Known Food borne Enteric Viruses of Known Epidemiological SignificanceEpidemiological Significance

-Most severe of the foodborne viral diseases

-Approximately 5% of cases are food borne

- Reoviridae

- Important cause of infant diarrhea world-wide with relatively high mortality

- Food borne transmission rare

- Leading cause of viral food borne disease; leading cause of food borne disease?

- 20-80% of cases are transmitted by contaminated foods

Hepatitis A virus NorovirusesRotavirus

Human Noroviruses Human Noroviruses (HuNoV)(HuNoV)

CalcivirideaCalciviridea Five generaFive genera

SapovirusSapovirus NorovirusNorovirus

Multiple genogroupsMultiple genogroups GIGI GIIGII

Many genotypesMany genotypes Clinical featuresClinical features

From: Bank-Wolf et al., 2010Donaldson et al., 2010

Epidemiological Importance of HuNoV

Role of HuNoV in global burden of disease•Most common cause of acute gastroenteritis in

industrialized countries (Glass et al., 2010)•Leading cause of food borne disease (~50% of

outbreaks of confirmed etiology in US) (CDC, 2009, 2010)

•Likely responsible for much food borne disease of “unknown etiology”

•Role of personal hygiene (>56%) (Widdowson et al., 2005)

Why are Noroviruses Such Why are Noroviruses Such a Big Problem? a Big Problem?

Features of the virus Features of the virus Features of the host Features of the host Virus-Host interactionsVirus-Host interactionsDetection and control issues Detection and control issues ConclusionsConclusions

Features of the Virus

Capsid structure provides: Environmental persistence Resistance to inactivation

RNA genome provides: High error rate and lack of

proof-reading mechanism results in:• Mutation• Recombination

From: Duizer and Koopmans, 2007

Noroviruses

Persistence and Resistance: Persistence and Resistance: Epidemiological EvidenceEpidemiological Evidence

3 month durationPerson-to-person spreadPropagated outbreak despite extensive infection control measures From: CDC, 2009

GII NoV Persistence on Surfaces (by RT-qPCR)

NoV GII Persistence and NoV GII-RNA stability on industrial surfaces

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NoV GII Persistence and NoVGII-RNA stability on lettuce

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Disinfection EfficacyHypochlorite Disinfection (RT-qPCR)

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NV GII.4 MNV-1FCV

Ethanol Disinfection (RT-qPCR)

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FCV

Log10 NV reduction after exposure to dry, hand sanitizer, liquid soap and water rinse

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Figure. The mean log10 NV reduction measured by Taqman real-time PCR for three hand wash agents. HS: hand sanitizer LS: liquid soap WR: water rinse.

Host Features: Susceptibility

Genetics and acquired immunity

Genetics Histo blood group antigens

(HBGAs) and FUT-2 secretor status

Virus-specific Host cell binding receptor or co-

receptor Acquired Immunity

Short-term (months) No long-term (years) Some, but not broad, cross

protection Opportunities for vaccination?

From: Donaldson et al., 2010

Virus-Host Interactions: Dose-Response Relationships

Some probability of infection (although low) at <100 quantifiable genome copies

Infection in 50% of susceptible individuals at ~5 x 103 quantifiable genome copies

How much fecal matter? 1 g feces = 108 genome copies Need about 103 for 50% infection risk 0.00001 g

Source: Teunis et al., 2008

Fecal Shedding of HuNoVAcute Phase

Strain dependentGenogroup I: ~105-106 genomic units/gGenogoup II: ~108 genomic units/gGenogroup II.4 (epidemic): ~1010 genomic units/g

Statistically associated with duration of diarrhea (2 log10)

Asymptomatic food handlersConvalescent phase

Sources: Lee et al., 2007; Chan et al., 2006

Detection IssuesDetection Issues It’s complicated!It’s complicated!

Availability of viruses Availability of viruses Inert in foodsInert in foods Inability to culture Inability to culture in vitroin vitro Requires concentration, purification, and Requires concentration, purification, and

molecular detectionmolecular detection Relationship (or lack thereof) between Relationship (or lack thereof) between

viability (infectivity) and molecular detectionviability (infectivity) and molecular detection Surrogates?Surrogates?

The result: No reliable commercial The result: No reliable commercial method to detect HuNoV in feces, the method to detect HuNoV in feces, the environment, or foodsenvironment, or foods

Control IssuesControl Issues HuNoV persistenceHuNoV persistence

• 44ooC/60 days (<50% inactivation)C/60 days (<50% inactivation)• Complete inactivation 21Complete inactivation 21oo C/14-28 d (or more), 37 C/14-28 d (or more), 37oo C/1- C/1-

10 d 10 d HuNoV resistance to sanitizersHuNoV resistance to sanitizers

• Hypochlorite, iodine, gluteraldehyde effectiveHypochlorite, iodine, gluteraldehyde effective• Quats, ethanol, anionic detergents less effectiveQuats, ethanol, anionic detergents less effective

HuNov resistance to processesHuNov resistance to processes• HeatHeat• Ionizing radiationIonizing radiation• High pressureHigh pressure

The “Perfect” Pathogen?The “Perfect” Pathogen?

Tendency to evolve/emerge yields new strains, Tendency to evolve/emerge yields new strains, many co-circulating strainsmany co-circulating strains

Complex, incomplete and short-lived immunity Complex, incomplete and short-lived immunity means constant pool of susceptible personsmeans constant pool of susceptible persons

Low infectious does and high levels of virus in Low infectious does and high levels of virus in feces facilitates transmissionfeces facilitates transmission

Shedding in vomitus exacerbates the problemShedding in vomitus exacerbates the problem Persistence in the environment results in long-Persistence in the environment results in long-

term exposureterm exposure Difficulties in inactivation exacerbates the Difficulties in inactivation exacerbates the

problemproblem

Hepatitis E virus

Severe disease, esp. in pregnant women

Developing countries Waterborne Outbreak and sporadic

Industrialized countries Travelers (cruise ship

outbreak) Recently, autochthonous Potentially zoonotic?

From: Aggarwal and Naik, 2009

Worldwide Distribution of HEV Genotypes in Human Populations

From: Aggarwal and Naik, 2009

Other Gastointestinal Viruses? Perhaps causes of food borne disease of

“unknown” etiology Other members of the Picornaviridae family (human

enteroviruses, coxsackieviruses) Enteric adenoviruses Astroviruses Sapoviruses Probably many others (parvoviruses, enteric

coronaviruses, Bocaviruses) Current data based on analysis of fecal specimens

of patients presenting with acute gastroenteritis

Control of Viruses n Foods: Where We Are?

Increased recognition of the role of viruses in food borne disease

Food handling appears to be the most common source of contamination

AVOID HUMAN FECAL CONTAMINATION!! Hand-washing (soap and warm water) is best

control to date if implemented appropriately and frequently

Exclusion of food handlers with suspicious symptoms

Rigorous surface disinfection (high concentrations of chlorine) for vomiting incidents or fecal contamination

Control of HuNoV in Foods: Where We Need to Be

Cultivable human strain (HuNoV) More effective prevention and control strategies

• Better hand and surface sanitizers• Improved hygiene compliance on the part of food

handlers• Alternative indicators• Processes• Vaccines?

Commercial detection methods• Clinical• Food and Environmental

Acknowledgements Students and Staff

• Dr. Helen Rawsthorne (Lab Manager)• Dr. Doris D’Souza, Dr. Amir Mokhtari, Dr. Julie

Jean (Post-Docs)• Dr. Blanca Escudero-Abarca (lead scientist)• Many students: Alissa Dix, Paris Leggitt, Dr.

Arnie Sair, Dr. Efstathia Papafragou, Grace Tung, Matthew Moore, You Li

Collaborators• Dr. Christine Moe (Emory University)• Dr. Jan Vinje (CDC)

Funding Agencies• ILSI-NA• USDA Food Safety Safety Research Programs• NC Agricultural Service and Foundation