Transcript Slide 1

Norovirus
Controlling an Outbreak
Melissa Vaccaro
Program Specialist
PA Department of Agriculture
[email protected]
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.
Bar = 50 nanometers
Source: CDC Norovirus Technical Fact Sheet. See
http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirusfactsheet.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:
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institutions,
schools,
military operations,
hotels,
recreational camps, or
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).
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1990 1993 1996 1999 2002 2005
Number of
Norovirus
Outbreaks
Selected Published Foodborne
Norovirus Outbreaks Associated with
Different Settings
Workplace,
office setting
(10.7%)
Multiple
locations/
undetermined/
other (11.1%)
Catered
(15.8%)
Restaurant/deli
(28.9%)
Prison (0.35%)
Nursing home,
etc. (9%)
Fair (1.1%)
Private home
(7.3%)
Cruise ship
(6.8%)
School (6.9%)
Church; temple.
etc. (2.7%)
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
Salad
26
Produce/fruit
17
Sandwiches
13
Meat dishes
11
Bakery
products
7
Fish dishes
5
Oysters
3
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
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 fecaloral 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. 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
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.
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.
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.
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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
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)
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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
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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
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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
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
•Presence of feces and viral aggregation
on surfaces prolongs NoV survival
NoV Survival on Hard Surfaces
Surface
Temp.
39.2°F
71.6°F
86°F
NoV Survival
Time
7 days 5 days < 24
hrs
What does NoV like?
Cool
Dark
Moist
Anaerobic, although not necessary
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??
NoV Environmental Contamination
Environmental surface tests--Hotel outbreak
(Cheeseborough, 2000)
Surface
# Pos.
Carpets (known recent vomit)
5 of 8
% Pos
62%
Carpets (no known recent vomit)
Toilet rims/seats
Toilet handles, taps, basins & surfaces
9 of 12
8 of 11
13 of 39
75%
73%
39%
Horizontal surfaces below 1.5m (railings,
switches, table tops, counters, ‘phones)
Horizontal surf. (light fittings, switches,
wardrobe tops, counter tops) above 1.5m
11 of 29
37%
6 of 12
50%
Phones, door handles, etc.
Soft furnishings, cushions, curtains, ect.
Total
7 of 29
24%
2 of 10
20%
61 of 144 42%
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
Wash and dry produce as much as possible, without
direct human contact, & avoid dark, anaerobic storage
conditions
Effective Disinfectants for NoV
Disinfectant
Conc./ Contact Time Surface/Product
Hypochlorous
Acid solution
(85-98% HOCl)
188ppm/ 1 min.
SodiumHypochlorate
5000ppm/ 1 min. (25
from 5.25%
tablespoons of household
Bleach Soln.
bleach [5.25%] per gallon of
Reference
Stainless steel; ceramic
tiles
Park et al.,
2007
Melamine (plastics)
Barker, 2003
water)
UV
For FCV: 254 nm UV @
19.04 mW s cm-2 or For
MS2: 254 nm UV @ 62.50
mW s cm-2
Waste Water:
secondary effluent
Tree, et al.,
2005
High hydrostatic
pressure
400-MPa at 5°C
Oysters
Kingsley et
al., 2007
Heat
158°F/ 5 min., or
212°F/ 1 min.
Carpet; upholstered
furniture
MIDCH,
2007
Effective Treatments Against NV Continued:
Disinfectant
Conc./ Contact
Time
Ozone gas
0.37mg/l/ 10 sec. Contaminated
water
Soap & Water
Handwash
Surface/Product
Reference
Shin and
Sobsey,
2003
20-25 ppm/ 20
min.
Office; hotel room; Hudson et
cruise ship settings al., 2007
1ml bland ivory
soap/ 20 sec.
Hands
Bidawid et
al., 2004
Points of Concern
Quaternary Ammonia is not effective on nonenveloped 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.
Conclusion
Understanding the survival and
transmission of NoV outside of the host
can help us develop effective control
mechanisms