Presentation on theme: "Norovirus Controlling an Outbreak Melissa Vaccaro Program Specialist PA Department of Agriculture"— Presentation transcript:
Norovirus Controlling an Outbreak Melissa Vaccaro Program Specialist PA Department of Agriculture
Norovirus Bar = 50 nanometers 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 factsheet.htm
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, institutions, schools, schools, military operations, military operations, hotels, hotels, recreational camps, or recreational camps, or aboard cruise ships aboard cruise ships
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
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
Potential Transmission Level Norovirus 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 1-10 viral particle (Teunis & Moe, 2008).
Selected Published Foodborne Norovirus Outbreaks Associated with Different Settings
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 Food Item % of NoV Outbreaks Salad26 Produce/fruit17 Sandwiches13 Meat dishes 11 Bakery products 7 Fish dishes 5 Oysters3
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
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 Person-to-Person: Important means of sustaining & spreading an outbreak Environment-to-Person: Important means of sustaining & spreading an outbreak
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
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
Hand contamination De Wit, et al Examined the fecal contamination level of the hands, after handwashing (E.coli as an indicator). 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 Found E.coli in 25% of sampled individuals after stools
Hand ContaminationDe Wits 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.
Hand Transmission Hand contamination study: 14 out of 14 people contaminated by touching the same door handle, one after the other 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 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. Shaking hands with 1 contaminated person contaminated 6 other people.
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 Telephone in living room Drawer handles in kitchen and bathroom Drawer handles in kitchen and bathroom Water faucet in kitchen and bathroom Water faucet in kitchen and bathroom Light switch in kitchen Light switch in kitchen Refrigerator handle in kitchen Refrigerator handle in kitchen Bar of Soap Bar of Soap Teapot Handle Teapot Handle
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 can transfer sequentially to 4 different surfaces Detergent cleaning, followed by rinsing was not effective in cleaning contaminated surfaces, unless followed with a disinfectant.
NoV Potential Sources Contaminated Soil Flood Waters On Site Disposal Systems Septic Tanks Septic Tanks Estimated that 40% are not functioning properly
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 of 59°F or 15°C (moisture levels of 25-15%): 92 days Winter field conditions of 59°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 Summer field conditions of 27-33°C or 80.6 – 91.4°F (moisture levels of 3-40%): 1.2 days
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
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
NoV Survival on Hard Surfaces Surface Temp. 39.2°F71.6°F86°F NoV Survival Time 7 days 5 days < 24 hrs Presence of feces and viral aggregation on surfaces prolongs NoV survival
What does NoV like? CoolDarkMoist Anaerobic, although not necessary
Conditions That Support NoV Survival on Produce CoolDarkMoist 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??
NoV Environmental Contamination Environmental surface tests--Hotel outbreak ( Cheeseborough, 2000) ( Cheeseborough, 2000) Surface # Pos. % Pos Carpets (known recent vomit) 5 of 8 62% Carpets (no known recent vomit) 9 of 12 75% Toilet rims/seats 8 of 11 73% Toilet handles, taps, basins & surfaces 13 of 39 39% Horizontal surfaces below 1.5m (railings, switches, table tops, counters, phones) 11 of 29 37% Horizontal surf. (light fittings, switches, wardrobe tops, counter tops) above 1.5m 6 of 12 50% Phones, door handles, etc. 7 of 29 24% Soft furnishings, cushions, curtains, ect. 2 of 10 20% Total 61 of %
Interrupting Human Transmission Pathway Control 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 environmental surfaces Restrooms are Reservoirs Restrooms are Reservoirs Wash and dry produce as much as possible, without direct human contact, & avoid dark, anaerobic storage conditions
Effective Disinfectants for NoV DisinfectantConc./ Contact TimeSurface/ProductReference Hypochlorous Acid solution (85-98% HOCl) 188ppm/ 1 min. Stainless steel; ceramic tiles Park et al., 2007 SodiumHypochlorate from 5.25% Bleach Soln. 5000ppm/ 1 min. ( 25 tablespoons of household bleach [5.25%] per gallon of water) Melamine (plastics) Barker, 2003 UV For FCV: 254 nm mW s cm -2 or For MS2: 254 nm mW s cm -2 Waste Water: secondary effluent Tree, et al., 2005 High hydrostatic pressure 400-MPa at 5°COysters Kingsley et al., 2007 Heat158°F/ 5 min., or 212°F/ 1 min. Carpet; upholstered furniture MIDCH, 2007
Ozone gas0.37mg/l/ 10 sec.Contaminated water Shin and Sobsey, ppm/ 20 min. Office; hotel room; cruise ship settings Hudson et al., 2007 Soap & Water Handwash 1ml bland ivory soap/ 20 sec. Hands Bidawid et al., 2004 DisinfectantConc./ Contact Time Surface/ProductReference Effective Treatments Against NV Continued:
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 dont 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.
Conclusion Understanding the survival and transmission of NoV outside of the host can help us develop effective control mechanisms