Transcript Foodborne Viruses:IFT'98

Noroviruses and Food borne Disease:
A Little Pathogen that Causes Big
Problems
Lee-Ann Jaykus, Ph.D.
Professor and IAFP President
What are the Human Enteric Viruses?

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Obligate intracellular parasites
Simple structure, RNA genome
Very small
Transmitted by humans
•
•
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Feces
Vomitus (Norovirus)
Highly transmissible
Difficult to:
•
•
Study
Detect
Duizer and
Koopmans,
2007
Sources of Exposure to Enteric
Viruses
Drinking Water
FOODS
VIRUS TRANSMISSION
Person-to-Person
“Direct” (fecal)
“Indirect” (vomitus)
Fomites
Other
Recreational waters
Soil
At-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)
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
Aug 13-14:
Sep 15:
Meat-slicer
ill
Median norovirus incubation
period (33 hours)
Sep 12:
Batch 1
withdrawn
Aug 18-23:
Batch 1 delivered
Guide ill
60
5
40
Aug 15-16
Batch 1
deli meat sliced
WELL TRIPS
Sep 17:
Other rafters ill
ILL TRIPS
Aug 19:
Rafting trips (N)
Ill Rafters
50
30
20
10
0
1
2
3
4
5
Trip Days
6
7
8
9
10
4
1st affected
trip
3
2
1
0
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
ug
ug
ug
ug ug
ug
ug
ug ug
-A 6-A 8-A 0-A 2-A 4-A 6-A 8-A 0-A 1-S 3-S 5-S 7-S 9-S 1-S 3-S 5-S 7-S 9-S
4
1
1
1
1
1
1
1
1
2
2
2
2
2
3
= Meat from “Batch 1” served on trip
Days (Aug 14 - Sep 19)
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
Epidemiological Significance
Hepatitis A virus
-Most severe of the
foodborne viral
diseases
-Approximately 5%
of cases are food
borne
Rotavirus
- Reoviridae
- Important cause of
infant diarrhea worldwide with relatively
high mortality
- Food borne
transmission rare
Noroviruses
- Leading cause of viral
food borne disease;
leading cause of food
borne disease?
- 20-80% of cases are
transmitted by
contaminated foods
Human Noroviruses (HuNoV)
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Calciviridea
Five genera
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Sapovirus
Norovirus
Multiple genogroups
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GI
GII
Many genotypes
 Clinical features
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From:
Bank-Wolf et al., 2010
Donaldson 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 a
Big Problem?
 Features
of the virus
 Features of the host
 Virus-Host interactions
 Detection and control issues
 Conclusions
Features of the Virus
 Capsid
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
Noroviruses
Environmental persistence
Resistance to inactivation
 RNA

structure provides:
genome provides:
High error rate and lack of
proof-reading mechanism
results in:
• Mutation
• Recombination
From: Duizer and Koopmans, 2007
Persistence and Resistance:
Epidemiological Evidence
3 month duration
Person-to-person spread
Propagated 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
4.5
4.5
Formica
SS
RNA Formica
RNA SS
3.5
4°C
22°C
RNA-4°C
RNA-RT
4
Log No. copies RNA/reaction
4
Log No. copies RNA/reaction
NoV GII Persistence and NoVGII-RNA stability on lettuce
3
2.5
2
1.5
1
0.5
3.5
3
2.5
2
1.5
1
0.5
0
0
0
5
10
15
20
25
Time (days)
30
35
40
45
0
2
4
6
8
Time (days)
10
12
14
16
Disinfection Efficacy
Hypochlorite Disinfection (RT-qPCR)
NV GII.4
MNV-1
e
FCV
g
e
g
NV GII.2
a
b
f
Ethanol Disinfection (RT-qPCR)
500ppm
MNV-1
d
d
NV GII.4
FCV
NV GII.2
a
c
b
e
e
e
%
90
%
%
70
Ethanol Concentration
50
%
90
%
70
%
50
%
90
%
70
%
%
a
90
%
b
b
50
a
70
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
-0.5
-1
%
Log Reduction
Chlorine Concentration
50
75ppm
500ppm
5ppm
f
d
250ppm
5ppm
1000ppm
500ppm
250ppm
75ppm
1000ppm
d
250ppm
b
75ppm
b
a
500ppm
a
250ppm
a
75ppm
Log Reduction
c
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
-0.5
-1
Log10 NV reduction after exposure to dry, hand sanitizer, liquid soap and water rinse
1.2
NV Log10 Reduction
1
Dry
HS
LS
WR
0.8
0.6
0.4
0.2
0
Dry
HS
LS
WR
Exposures
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
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Genetics and acquired immunity
Genetics
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Histo blood group antigens
(HBGAs) and FUT-2 secretor
status
Virus-specific
Host cell binding receptor or coreceptor
Acquired Immunity
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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
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Some probability of infection (although low) at
<100 quantifiable genome copies
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Infection in 50% of susceptible individuals at ~5 x
103 quantifiable genome copies
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How much fecal matter?
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1 g feces = 108 genome copies
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Need about 103 for 50% infection risk
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0.00001 g
Source: Teunis et al., 2008
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
Detection Issues
 It’s
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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
Control Issues
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HuNoV persistence
• 4oC/60 days (<50% inactivation)
• Complete inactivation 21o C/14-28 d (or more), 37o C/1-10 d
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HuNoV resistance to sanitizers
• Hypochlorite, iodine, gluteraldehyde effective
• Quats, ethanol, anionic detergents less effective
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HuNov resistance to processes
• Heat
• Ionizing radiation
• High pressure
The “Perfect” Pathogen?
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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
Hepatitis E virus
Severe disease, esp. in
pregnant women
 Developing countries
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Waterborne
Outbreak and sporadic
Industrialized countries
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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
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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
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Collaborators
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Funding Agencies
• 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
• Dr. Christine Moe (Emory University)
• Dr. Jan Vinje (CDC)
• ILSI-NA
• USDA Food Safety Safety Research Programs
• NC Agricultural Service and Foundation