Noroviruses and Food borne Disease: A Little Pathogen that Causes Big Problems

1. Noroviruses and Food borne Disease:A Little Pathogen that Causes Big Problems Lee-Ann Jaykus, Ph.D. Professor and IAFP President

2. What are the Human Enteric Viruses? • Obligate intracellular parasites • Simple structure, RNA genome • Very small • Transmitted by humans • Feces • Vomitus (Norovirus) • Highly transmissible • Difficult to: • Study • Detect

3. Duizer and Koopmans, 2007

4. Sources of Exposure to Enteric Viruses

5. At-Risk Foods • Molluscan Shellfish • Fresh Produce • Ready-to-Eat Foods •Others

6. Grand Canyon Outbreak Source: Malek et al., 2009

7. Food borne Enteric Viruses of Known Epidemiological Significance Hepatitis A virus Rotavirus Noroviruses • Leading cause of viral food borne disease; leading cause of food borne disease? • 20-80% of cases are transmitted by contaminated foods • 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

8. Human Noroviruses (HuNoV) From: Bank-Wolf et al., 2010 Donaldson et al., 2010 • Calciviridea • Five genera • Sapovirus • Norovirus • Multiple genogroups • GI • GII • Many genotypes • Clinical features

9. 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)

10. Why are Noroviruses Such a Big Problem? • Features of the virus • Features of the host • Virus-Host interactions • Detection and control issues • Conclusions

11. 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 Noroviruses From: Duizer and Koopmans, 2007

12. Persistence and Resistance: Epidemiological Evidence 3 month duration Person-to-person spread Propagated outbreak despite extensive infection control measures From: CDC, 2009

13. GII NoV Persistence on Surfaces (by RT-qPCR)

14. Disinfection Efficacy

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

16. 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

17. 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

18. Fecal Shedding of HuNoV • Acute Phase • Strain dependent • Genogroup I: ~105-106 genomic units/g • Genogoup II: ~108 genomic units/g • Genogroup II.4 (epidemic): ~1010 genomic units/g • Statistically associated with duration of diarrhea (2 log10) • Asymptomatic food handlers • Convalescent phase Sources: Lee et al., 2007; Chan et al., 2006

19. Detection Issues • It’s complicated! • Availability of viruses • Inert in foods • Inability to culture in vitro • Requires concentration, purification, and molecular detection • Relationship (or lack thereof) between viability (infectivity) and molecular detection • Surrogates? • The result: No reliable commercial method to detect HuNoV in feces, the environment, or foods

20. Control Issues • HuNoV persistence • 4oC/60 days (<50% inactivation) • Complete inactivation 21o C/14-28 d (or more), 37o C/1-10 d • HuNoV resistance to sanitizers • Hypochlorite, iodine, gluteraldehyde effective • Quats, ethanol, anionic detergents less effective • HuNov resistance to processes • Heat • Ionizing radiation • High pressure

21. The “Perfect” Pathogen? • Tendency to evolve/emerge yields new strains, many co-circulating strains • Complex, incomplete and short-lived immunity means constant pool of susceptible persons • Low infectious does and high levels of virus in feces facilitates transmission • Shedding in vomitus exacerbates the problem • Persistence in the environment results in long-term exposure • Difficulties in inactivation exacerbates the problem

22. 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

23. Worldwide Distribution of HEV Genotypes in Human Populations From: Aggarwal and Naik, 2009

24. 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

25. 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

26. 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

27. 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