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Norovirus Controlling an Outbreak

Norovirus Controlling an Outbreak. Melissa Vaccaro Program Specialist PA Department of Agriculture mvaccaro@state.pa.us. Norovirus. Single stranded, non-enveloped RNA virus belonging to the family Caliciviridae. July 1997 to June 2000 : 232 NoV outbreaks reported to CDC:

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Norovirus Controlling an Outbreak

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  1. NorovirusControlling an Outbreak Melissa Vaccaro Program Specialist PA Department of Agriculture mvaccaro@state.pa.us

  2. Norovirus Single stranded, non-enveloped RNA virus belonging to the family Caliciviridae • July 1997 to June 2000: 232 NoV outbreaks reported to CDC: • 57% were foodborne, • 16% were due to person-to-person spread, and • 3% were waterborne; in • 23% undetermined cause. • Source: CDC Norovirus Technical Fact Sheet. See http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus-factsheet.htm Bar = 50 nanometers

  3. NoV The Public Health Problem • Secondary Infections: Attack rate >50% in areas where a large population is enclosed within a static environment, such as: • institutions, • schools, • military operations, • hotels, • recreational camps, or • aboard cruise ships

  4. NoV The Public Health Problem • NoV is the most common cause of gastroenteritis in people of all ages • Responsible for almost 50 % of all foodborne gastroenteritis outbreaks and • 35% of all sporadic gastroenteritis outbreaks • Estimated to be as frequent a cause of illness and death internationally as Salmonella foodborne illness • The most significant diarrheal virus in terms of work/education days lost because it impacts all ages

  5. Characteristics of NoV • Acute onset of vomiting (often explosive) and diarrhea (also often explosive) • Typically Lasts only 24 to 48 hours & rarely fatal, • Seasonal virus: Peaks in Winter (Dec.- March) • Can have a serious impact on healthy individuals of all ages, resulting in hospitalization and even intensive care, and • Has been associated with serious complications or even fatalities in the elderly and immune compromised

  6. Potential Transmission LevelNorovirus • Shed in the feces at levels up to 1 Trillion viral particles per gram of feces. • One projectile vomiting incident can potentially contaminate the environment with 30,000,000 viral particles. • Infectious dose of NoV is now estimated to be as low as 1-10viral particle (Teunis & Moe, 2008).

  7. Selected Published Foodborne Norovirus Outbreaks Associated with Different Settings

  8. Source of NoV Outbreaks Reported to CDC (1991 – 2000) • Of the 76 outbreaks reported to CDC between 1991 to 2000 (for which data was complete and implicated foods), (Widdowson et al., 2005). • 43% outbreaks probably had some type of produce/fruit

  9. Risk of NoV Transmission • Vomiting vs. Diarrhea: No Difference in risk of secondary transmission in the home vs a non home setting. • The more primary cases sick: the > secondary illness rate

  10. Transmission of Norovirus • Fecal-Oral Route: Primary route responsible for causing foodborne outbreaks • Airborne Inhalation of microscopic droplets: Aerosols enhance dissemination of NoV in the environment during an outbreak; has been important means of transmitting NoV to staff • Person-to-Person: Important means of sustaining & spreading an outbreak • Environment-to-Person: Important means of sustaining & spreading an outbreak

  11. Environment-to-Person & Person-to-Person Norovirus Transmission • Contaminated surfaces are the most likely factor responsible for sustaining a succession of outbreaks • Hands play a significant role in NoV transmission, either through direct fecal-oral contact, or through the contamination of ready-to-eat food items

  12. NoV Survival on Hands • If = to HAV: about 4 hrs • Studies have shown at least 20 minutes 20 min – 4 hrs : survival rate on Hands

  13. Hand contaminationDe Wit, et al. 1992 • Examined the fecal contamination level of the hands, after handwashing (E.coli as an indicator). • Found E.coli in 25% of sampled individuals after stools

  14. Hand Contamination—De Wit’s studies Continued • Handwashing decreased the E.coli counts on the hands, but did not eliminate it. • Concluded that infected individuals shedding at high levels will have high hand contamination levels, even with hygiene practiced.

  15. Hand Transmission Hand contamination study: • 14 out of 14 people contaminated by touching the same door handle, one after the other • 13 out of 14 people contaminated by shaking hands with one contaminated hand one after another • Shaking hands with 1 contaminated person contaminated 6 other people.

  16. Hand Transmission • 1 door handle of an apartment shared by 4 students was intentionally contaminated: • Spread throughout room---all surfaces tested. Contamination found on all hands even after handwashing within 6 hrs. • Telephone in living room • Drawer handles in kitchen and bathroom • Water faucet in kitchen and bathroom • Light switch in kitchen • Refrigerator handle in kitchen • Bar of Soap • Teapot Handle

  17. Transfer from Contaminated Fingers • Barker (2004) found that NoV can transfer from contaminated fingers, sequentially to 7 different environmental surfaces • Secondary Transfer of NoV (from contaminated surfaces to clean fingers, to other surfaces) • can transfer sequentially to 4 different surfaces • Detergent cleaning, followed by rinsing was not effective in cleaning contaminated surfaces, unless followed with a disinfectant.

  18. NoV Potential SourcesContaminated Soil • Flood Waters • On Site Disposal Systems • Septic Tanks • Estimated that 40% are not functioning properly

  19. NoV Survival in Soil • At least 12 weeks were required for a 99% reduction of HAV in soil at 41°F or 5°C. • Reported viral decay • Winter field conditions of59°F or 15°C (moisture levels of 25-15%): 92 days • Summer field conditions of 27-33°C or 80.6 – 91.4°F (moisture levels of 3-40%): 1.2 days

  20. NoV Stability/Survival in Water • Survives freezing conditions • Survives exposure to acidity levels below pH 3 • Presence of feces and viral aggregation prolongs NoV survival • Survives in Salt water (0.5 and 1 M NaCl) for >6 days at room temperature (75.2°F) • Survives in dechlorinated water for 25 days at 39.2°F and for 18 days at 77°F • Inactivated by boiling at 212ºF • May survive up to 1 year in bottled drinking water stored in the dark. • Impacted by microbial antagonism, sunlight, warmer temperature and the presence of oxygen

  21. NoV Stability/Survival in Food • Survives freezing conditions • Survives heating at 140°F/ 60 ºC for 30 minutes—Inactivated by boiling at 212°F/ 100 ºC • Impacted by warmer temperature, sunlight, and oxygen • Survives exposure to acidity levels below pH 3 • Survives better under wet conditions than dry conditions • Survives on produce longer than the shelf life of the produce item under refrigerated temperatures. • May be susceptible to high pressure processing

  22. NoV Survival on Hard Surfaces • Presence of feces and viral aggregation on surfaces prolongs NoV survival

  23. What does NoV like? • Cool • Dark • Moist • Anaerobic, although not necessary

  24. Conditions That Support NoV Survival on Produce • Cool • Dark • Moist • Anaerobic (without Oxygen) Storage under these conditions reduces viral decay and enhances survival rates • 43% outbreaks probably had some type of produce/fruit involvment • Remember peak rate is in Winter??

  25. Interrupting Human Transmission PathwayControl Measures • Handwashing & prohibiting bare hand contact with RTE food items is critical • Removing food workers with active vomiting and/or diarrhea is critical • Reducing airborne transmission • Treat as infectious material • Cleaning Staff should use barriers, such as face masks, gloves, and aprons. • Dispose materials used to clean-up vomiting incident, and thoroughly disinfect the area. • Properly disinfect contaminated environmentalsurfaces • Restrooms are Reservoirs • Wash and dry produce as much as possible, without direct human contact, & avoid dark, anaerobic storage conditions

  26. Effective Disinfectants for NoV

  27. Effective Treatments Against NV Continued:

  28. Points of Concern • Quaternary Ammonia is not effective on non-enveloped viruses such as NoV • Hand Sanitizers (alcohol based) are NOT effective on NoV---Does kill Flu virus • Contain as much of the “mess” as possible—don’t spread more • MUST DISINFECT APPROPRIATELY!!! • If a food contact surface: follow disinfectant with a potable water rinse after air drying to make the are safe for food contact again.

  29. Conclusion Understanding the survival and transmission of NoV outside of the host can help us develop effective control mechanisms

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