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Title: Ewen C. D. Todd


1
What We Can Learn from the Role of the Food
Worker in Outbreaks
  • Ewen C. D. Todd
  • Advertising, Public Relations and Retailing
  • Michigan State University
  • Train the Trainer Workshop at the International
    Food Safety Conference
  • Dubai, February 2009

2
What Have We Learned from Investigation of
Outbreaks Where Food Workers Were Implicated?
3
Impact of the Infected Food Worker
  • CDC estimates 76 million cases of foodborne
    illness each year in the United States
  • Estimated that between 18-20 of foodborne
    illness associated with an infected food worker
    in the US, and 7 of salmonellosis in the UK
  • Thus, there may be up to 13-15 million cases in
    the US associated with an infected food worker
    (18-20 of 76 million)

4
Definition of Food Worker
  • The term food worker is used in this context to
    describe individuals, who harvest, process,
    prepare and serve food
  • It is broader in context than food handler
    although the two terms are used interchangeably
    in the literature and investigative reports

5
Purpose of Study of Infected Food Workers
Implicated in Outbreaks
  • Project of the Committee on Control of Foodborne
    Illness (CCFI) of the International Association
    for Food Protection (IAFP)
  • Goal to develop an understanding of the dynamics
    of transmission of infectious agents to and from
    the food worker in a variety of settings
  • The CCFI approached the task with the premise
    that all foodborne illness is fundamentally
    preventable and that by influencing human
    behavior there will be fewer opportunities for
    spread of infectious disease agents by workers
    and others

6
Papers Prepared on Outbreaks Where Food Workers
Have Been Implicated in the Spread of Foodborne
Disease in the Journal of Food Protection
(2007-2009)
  • Part 1 Description of the problem, methods and
    agents involved
  • Part 2 Description of outbreaks by size,
    severity, and settings
  • Part 3 Factors contributing to outbreaks and
    description of outbreak categories
  • Part 4 Infective doses and pathogen carriage
  • Part 5 Sources of contamination and pathogen
    excretion from infected persons
  • Part 6 Transmission and survival of pathogens in
    the food processing and preparation environment
  • Part 7 Barriers and sanitizers in reducing
    contamination
  • Part 8 Hand hygiene

7
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8
Outbreaks by Geographical Region
Geographical Region Number of Outbreaks () Number of Cases ()
USA 647 (79.3) 54,888 (68.0)
Europe 63 (7.7) 7,694 (9.5)
Canada 62 (7.6) 3,320 (4.1)
Australia/Asia 27 (3.3) 4,680 (5.8)
Latin America/Caribbean 6 (0.7) 5,408 (6.7)
Africa 4 (0.5) 2,394 (3.0)
Middle East 3 (0.4) 400 (0.5)
Multiple Countries 2 (0.2) 1,843 (2.3)
Unknown 2 (0.2) 55 (0.1)
Totals 816 (100) 80,682 (100)
9
Summary of Data on Pathogens
  • 816 outbreak reports with 80,682 cases
  • Pathogens in order of frequency
  • norovirus/probable norovirus (338)
  • Salmonella enterica (151)
  • hepatitis A virus (84)
  • Staphylococcus aureus (53)
  • Shigella spp (33)
  • Streptococcus pyogenes Group A (17)
  • Parasites Cyclospora, Giardia, and
    Cryptosporidium (23)

10
Outbreaks by Food Category
Commodity
11
Foods Associated with Outbreaks Where Food
Workers Were Implicated
  • Multiple foods and multi-ingredient foods were
    noted most frequently
  • Salads, including potato, pasta and coleslaw (92)
  • Sandwiches (74)
  • Chinese, Mexican type food, and pizza (19)
  • Hors doeuvres and other RTE cold snacks with
    sauces and glazes (8)

12
Outbreaks by Settings

Mainly restaurants
13
Most Extreme Outbreaks
  • Largest outbreak
  • 6350 cases 1987, North Carolina S. sonnei
  • Largest number hospitalized
  • 396 1998, Brazil S. aureus
  • Largest number of deaths
  • 68 1990, Mozambican refugees in Malawi V.
    cholerae

14
1 Single worker causes an outbreak that affects
patrons
2b Offsite food worker(s) infects other workers
at a different location
6 Food contaminated by offsite workers
2a, 4a, 4b, 5 Multiple workers cause outbreak at
the same location (2a), through contamination of
food (4a), no clear source (4b), or workers may
be the victims (5)
3a, 3b Foods contaminated by infected worker are
temperature abused leading to outbreak
8 Worker(s) are infected but deny illness and
outbreaks not reported as caused by infected
worker(s)
7 Infected consumers (patrons, families,
institutional residents, etc) likely source of
infectious agent
Ill Consumers (Patrons, Families, Institutional
Residents, etc)
15
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16
Social Gathering and Staphylococcus aureus
  • 8,000 people gathered in a community to celebrate
    a Catholic priests ordination in 1998 in Brazil
  • After eating food provided, 4,000 were acutely
    ill and 2,000 hospitalized, 16 died
  • Eight food workers began preparing the chicken,
    roast beef, rice, and beans over 48 h on the
    Friday before the event, and stored in aluminum
    containers at room temperature until Sunday
    morning
  • These food workers had positive fingernail swabs
    for Staphylococcus aureus, and five of them had
    the same strain isolated from their nasopharynxes
  • Leftover food was also found to contain S. aureus
    at 2.0 x 108 CFU/g, which produced 6 µg of
    enterotoxin A/g

17
Social Gathering and Staphylococcus aureus
  • 8,000 people gathered in a community to celebrate
    a Catholic priests ordination in 1998 in Brazil
  • After eating food provided, 4,000 were acutely
    ill and 2,000 hospitalized, 16 died
  • Eight food workers began preparing the chicken,
    roast beef, rice, and beans over 48 h on the
    Friday before the event, and stored in aluminum
    containers at room temperature until Sunday
    morning
  • These food workers had positive fingernail swabs
    for Staphylococcus aureus, and five of them had
    the same strain isolated from their nasopharynxes
  • Leftover food was also found to contain S. aureus
    at 2.0 x 108 CFU/g, which produced 6 µg of
    enterotoxin A/g

18
Examples of S. aureus Outbreaks
  • 2 handlers sores on hands, 5 handlers same strain
    in nose
  • S. aureus isolated from infected cut on hand of
    person who baked cake
  • 11 hospitalized S. aureus isolated from stool,
    vomitus, sandwich and infected finger of food
    handler, sandwiches stored 8-10 hours without
    refrigeration
  • S. aureus in food and on food handler, inadequate
    storage temperature for 5 hours
  • S. aureus phage 6 patients and 6 food handlers,
    infected cut on hand of one food worker who mixed
    food ingredients with bare hands
  • Cook handled and cooked ham with open cuts, sores
    and finger lesion
  • Contamination from hand of a symptomatic food
    worker, stored at inappropriate temperature

19
School Children and Norovirus
  • 3,236 (41.5) of 7,801 schoolchildren and 117
    (39.4) of 297 teachers were ill in Japan in 1989
    after eating catered food
  • Food had been provided by a catering company to
    nine elementary schools
  • Workers had bare-hand contact with the food, and
    a worker reported symptoms of gastrointestinal
    illness on the day the food was prepared

20
School Children and Norovirus
  • 3,236 (41.5) of 7,801 schoolchildren and 117
    (39.4) of 297 teachers were ill in Japan in 1989
    after eating catered food
  • Food had been provided by a catering company to
    nine elementary schools
  • Workers had bare-hand contact with the food, and
    a worker reported symptoms of gastrointestinal
    illness on the day the food was prepared

21
Frosted Cakes Leading to Norovirus Infections
  • A bakery worker in Minnesota in 1982 prepared 76
    litres of frosting using his arm up to the elbow
    to break sugar lumps and scrape the sides of the
    vat
  • There were subsequently 3,000 cases of norovirus
    infection
  • He had five episodes of diarrhea and two of
    vomiting during his 6-h shift when he frosted the
    cakes
  • Also he had sick children at home

22
Frosted Cakes Leading to Norovirus Infections
  • A bakery worker in Minnesota in 1982 prepared 76
    litres of frosting using his arm up to the elbow
    to break sugar lumps and scrape the sides of the
    vat
  • There were subsequently 3,000 cases of norovirus
    infection
  • He had five episodes of diarrhea and two of
    vomiting during his 6-h shift when he frosted the
    cakes
  • Also he had sick children at home

23
Giardiasis from Salad
  • In 1990, a food worker in the cafeteria of a
    large Connecticut insurance company was infected
    with Giardia lamblia and used her bare hands
    while slicing raw vegetables, causing 27 cases of
    giardiasis
  • She tested positive and had used gloves for most
    food preparation activities but not for salad bar
    items
  • The investigators noted that the outbreak was
    probably only detected because the affected
    individuals were insurance company employees
    whose medical care was administered by a single
    health management team

24
Giardiasis from Salad
  • In 1990, a food worker in the cafeteria of a
    large Connecticut insurance company was infected
    with Giardia lamblia and used her bare hands
    while slicing raw vegetables, causing 27 cases of
    giardiasis
  • She tested positive and had used gloves for most
    food preparation activities but not for salad bar
    items
  • The investigators noted that the outbreak was
    probably only detected because the affected
    individuals were insurance company employees
    whose medical care was administered by a single
    health management team

25
Hepatitis at a Resort
  • In 2004, a large outbreak with 351 hepatitis A
    cases occurred involving tourists at a specific
    hotel in the Egyptian resort city of Hurghada
  • Guests who developed HAV infection after their
    vacation were 2.6 times more likely to have
    ingested orange juice than were healthy controls
  • None of the hotel staff in Egypt was positive
  • The juice was not pasteurized and came from a
    site where hygiene problems were identified
  • Although an infected worker at the juice
    production company was the most likely source,
    none of the company staff was IgM positive, but
    staff members often changed and were not
    available for testing

26
Hepatitis at a Resort
  • In 2004, a large outbreak with 351 hepatitis A
    cases occurred involving tourists at a specific
    hotel in the Egyptian resort city of Hurghada
  • Guests who developed HAV infection after their
    vacation were 2.6 times more likely to have
    ingested orange juice than were healthy controls
  • None of the hotel staff in Egypt was positive
  • The juice was not pasteurized and came from a
    site where hygiene problems were identified
  • Although an infected worker at the juice
    production company was the most likely source,
    none of the company staff was IgM positive, but
    staff members often changed and were not
    available for testing

27
Norovirus in a Restaurant (1)
  • In Michigan in 2006, 364 restaurant patrons
    became ill with norovirus GI illness after dining
    at a restaurant where employees had reported to
    work while ill
  • On Jan 28, a line cook vomited at home before
    reporting to work at 1100 a.m. and then vomited
    again into a waste bin beside the frontline
    workstation at approximately 200 p.m. while
    preparing antipasti platters, pizzas, and salads
  • After vomiting, he remained on site (but off the
    cooking line) and left work at 415 p.m.
  • This cook also reported to work on Jan 29 from
    1100 a.m. to 430 p.m. while still experiencing
    loose stools
  • Because of the open physical layout of the
    restaurant, no barrier impeded airborne spread of
    the virus from the kitchen to the main dining area

28
Norovirus in a Restaurant (2)
  • There was a significant association between the
    platter and the ill persons
  • Patron attack rates increased after the cook
    vomited and among employees, particularly cooks
    vs. servers, who worked on Jan 28
  • The investigation revealed deficiencies in
    employee hand washing practices, cleaning and
    sanitizing of food and nonfood contact surfaces,
    temperature monitoring and maintenance of
    potentially hazardous food, and maintenance of
    hand-sink stations for easy accessibility and
    proper use
  • A quaternary ammonium based sanitizer normally
    used to clean the restaurant was ineffective
    against the norovirus
  • Then, a bleach solution used to disinfect the
    restrooms and all surface areas within at least a
    25-ft radius of the vomiting site was effective
    for preventing further illnesses

29
Norovirus in a Restaurant (1)
  • In Michigan in 2006, 364 restaurant patrons
    became ill with norovirus GI illness after dining
    at a restaurant where employees had reported to
    work while ill
  • On Jan 28, a line cook vomited at home before
    reporting to work at 1100 a.m. and then vomited
    again into a waste bin beside the frontline
    workstation at approximately 200 p.m. while
    preparing antipasti platters, pizzas, and salads
  • After vomiting, he remained on site (but off the
    cooking line) and left work at 415 p.m.
  • This cook also reported to work on Jan 29 from
    1100 a.m. to 430 p.m. while still experiencing
    loose stools
  • Because of the open physical layout of the
    restaurant, no barrier impeded airborne spread of
    the virus from the kitchen to the main dining area

30
Norovirus in a Restaurant (2)
  • There was a significant association between the
    platter and the ill persons
  • Patron attack rates increased after the cook
    vomited and among employees, particularly cooks
    vs. servers, who worked on Jan 28
  • The investigation revealed deficiencies in
    employee hand washing practices, cleaning and
    sanitizing of food and nonfood contact surfaces,
    temperature monitoring and maintenance of
    potentially hazardous food, and maintenance of
    hand-sink stations for easy accessibility and
    proper use
  • A quaternary ammonium based sanitizer normally
    used to clean the restaurant was ineffective
    against the norovirus
  • Then, a bleach solution used to disinfect the
    restrooms and all surface areas within at least a
    25-ft radius of the vomiting site was effective
    for preventing further illnesses

31
Norovirus from Salad
  • In 2000, a catered meal and distributed to 52 car
    dealerships in the US as a reward for high car
    sales was responsible for multiple
    gastroenteritis outbreaks in 13 states, resulting
    in at least 333 cases
  • Pasta salads from one caterer was strongly
    associated with illness
  • Pasta was placed in large plastic bins, other
    ingredients were added, and food workers mixed
    the salad by immersing their ungloved arms up to
    the elbow
  • Although the workers denied any history of
    illness in the preceding week, 2 of 15 employees
    had elevated IgA antibody titres to norovirus
  • This caterer had been cited by health inspectors
    for multiple sanitary code violations and was
    temporarily closed pending sanitary improvements

32
Norovirus from Salad
  • In 2000, a catered meal and distributed to 52 car
    dealerships in the US as a reward for high car
    sales was responsible for multiple
    gastroenteritis outbreaks in 13 states, resulting
    in at least 333 cases
  • Pasta salads from one caterer was strongly
    associated with illness
  • Pasta was placed in large plastic bins, other
    ingredients were added, and food workers mixed
    the salad by immersing their ungloved arms up to
    the elbow
  • Although the workers denied any history of
    illness in the preceding week, 2 of 15 employees
    had elevated IgA antibody titres to norovirus
  • This caterer had been cited by health inspectors
    for multiple sanitary code violations and was
    temporarily closed pending sanitary improvements

33
Characteristics of Pathogens
34
Infectivity of Pathogens Transmitted by Infected
Food Workers
Agent Incubat-ion Period In Days (mean) Carriage (C) Rates Reported () Presymp-tomatic Shedding Time (days) Sympto-matic Period (Days) Post-sympt-omatic Shedd-ing (days) Asymp-tomatic Overall Period of Infect-ivity (days) Source of Infectious Material Carriage/ Shedding
Norovirus 0.6-3.2 GI 1.1-1.5 Control 0.2 1.5? 1-11 2 weeks 32 May be gt2 weeks IT, F, RT, V
HAV 10-50 (28) 0.01 in population 10-14 7-14 21 (180) 8 (70 in elderly) Up to 8 weeks F, U
Salmon-ella 0.25-10 GI0-16 Control 0.1-1.6 X 7-10 4-22 weeks 0.23-10 19 for FWs in DCs Up to years IT, F
Shigella 0.5-6 GI 0-0.8 X 4-7 60-150 55 - 75 Up to years IT, F
S. aureus 2-6 hours 20-36 C C C 20 - 65 Years N, S, C
Giardia lamblia 3-25 (7) GI0.4-16 X 7-60 Up to 35 (children) Months IT, F
IT Intestinal Tract, RT Respiratory Tract, F
Feces, N Nasal Secretions, S Skin/Skin
Lesions, U Urine, V Vomitus
35
Foodborne Pathogens Transmitted by Infected Food
Worker and Periods of Infectivity
Time After Exposure (Days)
0
50
100
150
200
250
300
Norovirus (SRSV/NLV)
Hepatitis A
Salmonella spp.
S. Typhi/Paratyphi
Shigella spp.
Staphylococcus aureus
Streptococcus pyogenes
Giardia lamblia
Campylobacter jejuni
Cryptosporidium parvum
Vibrio cholerae
E. coli O157H7
Yersinia enterocolitica
Incubation
Incubation/ Pre-symptomatic
Pre-symptomatic Shedding Phase
Extended Symptomatic
Symptomatic Period
Post-symptomatic Phase
Extended Post-symptomatic Phase
Carrier State
36
Levels of Pathogens in Body Excretions
  • Salmonella in feces
  • Ill or early convalescence 105-107 CFU/g
  • Late excretion (infants excrete longer) 100-103
    CFU/g
  • 10-19 days after illness 100-106 CFU/g
  • 69-102 days after illness 100-104 CFU/g
  • Sneeze with Streptococcus pyogenes
  • up to 106 CFU/sneeze
  • up to 500 CFU/154 cm2 1.5 9.5 feet from sneeze
    source
  • HAV in feces just before hepatitis symptoms begin
  • 108 infectious particles/g
  • Norovirus in feces while ill
  • 105 1010 copies/g
  • Cryptosporidium in one bowel movement 108 109
    oocysts

37
Fecal Contamination of Hands During Toilet Use
With and Without Toilet Paper
  • Mean fecal weight/hand (g) after cleansing
  • Without toilet paper 8.5 x 10-6 - 9.8 x 10-7
  • With toilet paper 5.0 x 10-9
  • Pathogens can be present in feces at levels of
    from 105 to 1011 per g. A tenth of a milligram
    of fecal material (10-4 g), an amount barely
    perceptible, might contain up to a million
    infectious bacterial cells or viral particles
  • At 10-7 g fecal matter of contamination per hand
    and a pathogen that present at 1011 per g, if
    hands were washed and/or sanitized, a 2 to 3 log
    reduction (99-99.9) could still allow a worker
    to transmit a few cells
  • Add to the fact that those ill may be more
    careless with fecal cleanliness (continual
    cleanup from diarrhea, fecal accidents, and not
    focused on the job and hygienic practices), and
    the risk increases greatly

38
Survival of Enteric Pathogens on Hands and
Surfaces
Infective Agent Surfaces Log, Loss or Half Life
Salmonella Enteritidis in egg white and yolk Hands, inoculated eggs, formica surface, utensils Survived well 24 hrs.
Shigella sonnei Fecally- contaminated hands Survival for 3 hrs.
S. aureus Skin and clothing 1 log/5 hrs.
Campylobacter jejuni Hands with peptone, chicken broth, and 50 blood 3-7 log/ 2 min. 6 log/ 15 min. 6 log/ 45 min.
E. coli Skin 3 log/5 min.
E. coli in milk Fingertip 94 loss in 45 min.
Entamoeba histolytica Hands (nails in feces) Survival for 45 min.
39
Survival of Pathogens
  • Norovirus survived in carpets and toilet
    facilities for more than one day after an
    individual vomited on seats and washroom
    infected clean-up crew and subsequent concert
    hall attendees infected by aerosols
  • Illnesses from carpet removers in a hospital ward
    12 days after vomiting outbreak occurred
  • Pathogens tend to survive longer on surfaces such
    as ceramic tile, steel, dust, glass and plastic
    than on hands

40
Levels of Pathogens in Raw Meat and Poultry
Infective Agent Product Log 10 CFU
Campylobacter jejuni Chicken juices, ceca Chicken carcasses 103-109 lt101-109
E. coli O157H7 Ground beef Cattle/sheep feces 5 103-105
Salmonella Chicken juices, organ, carcasses Chicken fillets 102-106 lt10 with up to 103
41
Transfer of Organisms from Hands
  • The transfer efficiency between hands and lettuce
    was found to be 0.3 and from hands to spigots
    was 1
  • The transfer rate of HAV from fingerpads of adult
    volunteers to pieces of fresh lettuce was
    determined to be 9 of the infectious load on the
    fingers
  • Lettuce touched by a washed hand may be
    contaminated with as many as 3.8 log10 CFU
    indicator bacteria
  • A 10 transfer rate of bacteria from food to
    hands or bare hand to food and by using gloves,
    this rate was reduced to 0.01

42
Outbreaks Associated with Lack of Adequate
Hygienic Facilities
  • Inadequate toilet facilities (Yersinia,
    Shigella,Vibrio, Salmonella)
  • Non functional toilet (Shigella)
  • Lack of handwashing facilities (Shigella,Vibrio,
    HAV)
  • Inadequate handwash facilities (Shigella,
    norovirus)
  • Difficult to use faucets (HAV)
  • Lack of running water (Yersinia, Shigella,Vibrio)
  • Lack of fingernail brush (Giardia)
  • Lack of soap (Shigella,Vibrio, Giardia)
  • No paper towels for hand drying (Shigella,
    Salmonella, norovirus)

43
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44
Handwashing Occasions
  • Wash hands thoroughly with disinfectant soap and
    water at appropriate times for the job
    description
  • Also after the following
  • handing raw foods
  • after going to the toilet
  • after contact with persons suffering from acute
    GI symptoms
  • after being in contact with infants and
    incontinent individuals

45
Minimize Hand Contact
  • Evaluate food handling procedures and modify to
    reduce or eliminate hand contact for RTE food
  • Gloves
  • Utensils
  • Deli papers

46
Exclusion and Work Restrictions
  •  Exclude infected symptomatic persons (GI) from
    preparing and serving food during communicable
    periods of illness
  • Exclude infected persons known to be asymptomatic
    carriers based on screening
  • Restrict food workers from preparing or serving
    food
  • Infected skin lesions
  • Sore throat
  • Acute respiratory infections
  • Food workers should be kept on sick leave for 48
    h following disease cessation

47
Hygiene Education, Training and Supervision
  • Train food workers and supervisors
  • in proper food handling practices and procedures
  • to report personal and family illness
  • Provide supervision of workers
  • Surveillance of workers and correction of
    handling errors
  • Screen food workers (nasal and stool)
  • at start of employment
  • routine testing
  • upon return from travel in area having high
    endemic disease rates
  • Immunize workers when feasible (HAV, etc)

48
What Have Investigations of Outbreaks Where Food
Workers Were Implicated Taught Us - Sources?
  • There are many sources where food workers have
    become infected
  • Ill family members, homosexual partners or
    diapering a sick child
  • Intravenous drug use
  • Eating contaminated food
  • Environmental sources, e.g., water, animals
  • Travel abroad
  • Contact with other infected workers

49
Spread in the Food Worker Environment
  • Once a worker has brought an agent into a food
    operation, it can easily be transferred from
    person to person, person to food contact surfaces
    and to food
  • Lack of adequate handwashing facilities and
    improper handwashing and drying
  • Long and artificial nails are too difficult to
    clean effectively
  • Lesions and wounds harboring pathogens are not
    properly covered
  • Workers continuing to work when infected and ill
    (diarrhea and vomiting) management or worker
    decision
  • Transmission between workers in food preparation
    area
  • Lack of use of gloves/bare hand contact

50
Removal of Contaminants
  • Fecal contamination can be extensive even after
    washing use of toilet paper doesnt prevent all
    fecal organisms from going on finger tips and
    from there to contact surfaces
  • Vomiting can spread viral particles over long
    distances despite any clean up afterwards and
    particles can persist for days or weeks
  • Thorough and frequent handwashing and use of
    gloves keeps contamination in food environment to
    a minimum

51
Some Problems To Be Resolved
  • Having incentives for workers to stay home when
    they are ill or diagnosed with a likely infection
  • Identifying workers who are asymptomatic and need
    to be away from handling food and any physical
    contact with other workers
  • Effective communication with low-paid workers,
    often speaking other languages than English, may
    not read well and will move on for a continual
    turnover, issues of trust and motivation
  • Putting more resources into effective local
    investigation of outbreaks
  • More priorities for handwashing in industry/home

52
Acknowledgements
  • Bert Bartelson, Judy Greig, and Barry Michaels,
    members of the Committee for the Control of
    Foodborne Illness, International Association for
    Food Protection (IAFP), and IAFP Board

53
QUESTIONS?
54
Categorization of Outbreaks Where Food Workers
Were Implicated
  • 3. After food worker(s) contaminates food via
  • 3a) fecal contamination (e.g., by Salmonella,
    Shigella, Yersinia) or
  • 3b) through skin, nose and throat contamination
    (e.g., Streptococcus pyogenes, Staphylococus
    aureus)
  • Temperature abuse results in bacterial
    multiplication resulting in high enough numbers
    to cause illness

55
Categorization of Outbreaks Where Food Workers
Were Implicated
  • 4. Multiple food workers are
  • 4a) unequivocally the cause of the outbreak
    though contamination of food or food contact
    surfaces, or
  • 4b) linked to an outbreak but there is no clear
    initiating source
  • 5. Food worker(s) becomes infected but uncertain
    whether they are victims or causes of outbreak

56
Categorization of Outbreaks Where Food Workers
Were Implicated
  • 6. Food contaminated with pathogens by offsite
    workers and delivered to the location where the
    outbreak occurs by directly infecting
    consumers/patrons
  • Details of the worker contribution to the
    contamination are usually not known

57
Categorization of Outbreaks Where Food Workers
Were Implicated
  • 7. Patrons (those being served), not workers, are
    the probable source of the infectious agent
    though contamination of food or food contact
    surfaces
  • 8. Outbreaks where workers are implicated
    epidemiologically and likely are infected or
    colonized but deny illness

58
Category 1Single Worker Causes an Outbreak
  • 37 cases associated with cold salad bar items
    from the cafeteria of a Minnesota college, 2000
  • Index case a symptomatic food worker
  • Called in sick but symptoms resolved later that
    day
  • Returned to work the next day and worked the
    remainder of the week in salad bar section, with
    extensive bare-hand contact of salad items
  • Noroviral agent based on epidemiological
    information
  • Call-in ill log useful to determine dates that
    employees were ill and to ascertain the
    responsible employee

59
Category 2aMultiple Workers Cause Outbreak
  • Multi-state outbreak of Salmonella Thompson 78
    cases at fast food restaurants and catered events
  • Full-time employee did not wear gloves and
    handled every individual bread item at least
    twice
  • Worked with symptoms for 4 days until overnight
    hospitalization
  • Resumed work after discharge and continued
    working until termination of employment
  • She infected brother who also worked with dough
    and bread
  • No formal training on safe food-handling
    practices
  • Many employees spoke only Spanish but had English
    procedure manuals

60
Category 2b Offsite Food Worker(s) Infects
Workers at a Different Location
  • HAV affected 40 university students, 11
    employees of two restaurants, and 11 other
    residents in Arizona, 1973
  • Two distinct epidemic waves at the 2 restaurants
  • Index case of first restaurant prepared salads
  • Index case of the second restaurant had eaten at
    the first restaurant
  • Implicated vehicles at the second restaurant
    included guacamole, green salad, spaghetti, and
    hamburger

61
Category 3a Foods Fecally Contaminated by
Infected Worker are Temperature Abused Leading to
Outbreak
  • July 1981 New York Y. enterocolitica O8
    isolated from 37 persons including head cook and
    kitchen staff
  • Five hospitalized for appendicitis
  • Powdered milk and dispenser contaminated when
    food workers cleaned and repaired a broken spigot
  • Same strain isolated from chow mein indicating
    multiple contamination scenarios
  • Reconstituted milk held 24 hours under cool
    conditions but allowed growth of Yersinia

62
Category 3bFoods Nasally Contaminated by
Infected Worker are Temperature Abused Leading to
Outbreak
  • Convention in Florida 1979 outbreak of
    pharyngitis, 72/231 ill, including waiters and
    cooks
  • Streptococcus pyogenes Group G isolated from 10
    of 16 with pharyngitis and 1 of 41 who did not
  • Illness associated with chicken salad
  • Cook prepared chicken salad a day prior to her
    symptoms
  • Cooked chicken refrigerated overnight in a deep
    container
  • No indication she wore gloves or washed hands
    frequently
  • Opportunity for growth of the Streptococcus

63
Category 3b Foods Contaminated by Lesion of
Infected Worker and are Temperature Abused
Leading to Outbreak Commercial Travel
  • Flight attendant and 196 passengers rapidly
    developed vomiting and diarrhea following
    ingestion of ham and cheese omelets served during
    a chartered flight for a tour group from Tokyo to
    Paris, stopping en route in Alaska and Denmark
  • Cook who prepared ham had infected finger
  • Ham left at room temperature for six hours
  • S. aureus isolated from food samples

64
Category 4a Multiple Food Workers are
Unequivocally the Cause of the Outbreak
  • 2000 multi-state outbreak, 333 cases, catered
    meal prepared in Ohio and distributed to 52 car
    dealerships nationwide
  • Consumption of any of four side salads strongly
    associated with illness
  • Ingredients were placed in large plastic bins and
    mixed by food workers who immersed ungloved arms
    up to the elbow
  • 2 of 15 employees had elevated norovirus titers
  • Three food handlers were symptomatic before
    outbreak

65
Category 4b Multiple Food Workers are Linked to
Outbreak But There is No Clear Initiating Source
  • July 1992, 46 patrons at 21 restaurants in
    Michigan and one in Ohio infected with Shigella
    flexneri
  • Associated with consumption of pre-prepared
    salads from a central commissary
  • 15 infected workers ill during the same time
    period and four prepared salad during the
    outbreak period
  • Salad was mixed with bare hands, bagged by
    machine, and employees added or subtracted from
    the bags to meet the weight standard
  • Investigation failed to identify the infected
    employees

66
Category 5 Food Worker(s) Become Infected but
Uncertain Whether They Are Victims or Cause of
Outbreak
  • Large outbreak of shigellosis associated with a
    mass gathering in a national forest area, North
    Carolina, 1987
  • Over 50 of 12,700 attendees infected
  • Transmission assumed to be by food and water,
    followed by person-to-person contact
  • Food prepared in 47 communal kitchens with
    limited sanitation
  • Food from at least one kitchen implicated and
    unboiled water drunk by attendees

67
Category 6Food Contaminated With Pathogens by
Offsite Workers and Delivered to the Location
Where the Outbreak Occurs
.
  • Six norovirus outbreaks (1,143 cases) in
    institutions or commercial catering settings,
    June to Sept. 2005 in Denmark, linked to frozen
    raspberries imported from Poland
  • Unheated frozen raspberries served one day before
    start of each outbreak
  • Estimated 400 elderly people affected and at
    least 23 hospitalized
  • Three different norovirus serotypes isolated
  • Several independent contamination events likely
    occurred
  • Infected workers in the harvesting or processing
    of the raspberries in Poland were a likely but
    not proven source

68
Category 7 Patrons Are the Source of the
Infectious Agent Though Contamination of Food or
Food Contact Surfaces.
  • Mediterranean-style restaurant in Melbourne,
    Australia, three successive norovirus outbreaks,
    May 1998 - June 1999
  • Food served on platters and patrons ate with
    fingers, moving from table to table
  • Different norovirus strains isolated in the three
    outbreaks indicating no reservoir but recurring
    contamination of food
  • Demonstrates how norovirus can be transmitted
    where many people are in close contact and touch
    and eat food

69
Category 8 Outbreaks Where Workers Are
Implicated but They Deny Illness
  • Minnesota 2004 six relatives complained of GI
    illness after dining at a restaurant
  • 1 of 6 positive for norovirus
  • None of the workers were obviously symptomatic
  • Most of the staff were Spanish speaking and the
    manager acted as translator
  • Conclusion outbreak could not be adequately
    characterized even though the likely source of
    the norovirus was one or more employees

70
Examples of Streptococcus Outbreaks
  • Military base 3 food handlers of boiled egg
    salad were asymptomatic carriers of Streptococcus
    hand contamination or sneezing
  • Military base an egg salad preparer tested
    positive, he shelled boiled eggs with bare hands
    for the salad
  • School food preparer had open hand lesion that
    came in direct contact with the macaroni and
    cheese
  • Catered event preparer of egg salad had extreme
    cellulitis on hands he tasted the salad, workers
    coughed or sneezed

71
Examples of Hepatitis A Outbreaks
  • Salads
  • Restaurant two asymptomatic pantry workers
    contaminating food by hand shredding lettuce and
    dipping fingers into dressing to taste them
  • Caterer Salad boy with apparent good hygiene
    hand-tore moist lettuce and soon developed fever
    and malaise
  • Drinks
  • Employee, who was HAV positive but asymptomatic,
    was a suspected IV drug user, and had helped
    prepare fountain drinks and sandwiches
  • Bar tender had chronic diarrhea and contaminated
    the glasses when served beverages
  • Asymptomatic carrier did not wash his hands after
    using the toilet and contaminated the punch at a
    catered event 

72
Examples of Hepatitis A Outbreaks
  • Fast food restaurant food worker, who was a drug
    user and family described him as having poor
    hygiene, had diarrhea and tested positive for HAV
  • Caterer Asymptomatic sandwich maker had prior
    nausea and vomiting, most likely contamination
    through hand contact with foods
  • Caterer Pastry-cook had jaundice prior to
    preparing pastries by bare hand for meals
  • Bakery bakers assistant with hepatitis was
    directly involved in handling and dipping cooked
    pastries

73
Examples of Shigella Outbreaks
  • University Shigella infections after eating
    shrimp deveined in India contamination source
    uncertain but has to be human fecal
  • Restaurant employees ill with Shigella flexneri
    prepared tossed salad by reaching into chopped
    salad ingredients with bare hands
  • Restaurant worker infected with Shigella after a
    trip to Mexico washed lettuce with bare hands
  • Restaurant worker infected with Shigella
    flexneri in restaurant with hygiene violations,
    including a lack of hand washing between tasks
    and inadequate handwashing facilities

74
Examples of Salmonella Outbreaks
  • Salmonella enteritidis on curly fried potatoes
    and ice handled bare-handed by employee who had
    onset of illness 1 day prior, no paper towels
  • Prison Inmate who deboned turkey had multiple
    excoriated lesions on both forearms that had a
    positive S. aureus culture, Salmonella infantis
    isolated from turkey eaters

75
Examples of Norovirus Oubreaks
  • Salad asymptomatic noroviral shedding by one or
    more of the workers who handled lettuce with bare
    hands
  • RTE food hand preparation by untrained staff and
    patients
  • Catered function food worker excreted the virus
    and touched RTE foods including melon
  • Cruise ship ice machine did not have proper
    air-gap device to prevent sewage backup, and the
    ice was contaminated by hands of those scooping
    it out
  • Bakery A cake decorator, ill with GI, was
    wearing long artificial nails with which she
    contaminated the icing
  • Restaurant bad management forced employee to
    work, who was sick and wanted to stay home, used
    bare hands on hamburgers

76
Examples of Outbreaks Associated with Bare Hand
Contact
  • Restaurants
  • Bare hands serving pineapple slices, not ill at
    the time, but ill 3 hours after handling
  • Asymptomatic worker with no gloves sliced meats,
    cheese and vegetables, no adequate washing area
  • Symptomatic worker prepared guacamole and salsa
    with bare hands, good hand washing facilities
  • Employee excreting virus while using bare hands
    to remove tissues from steamed bovine heads
  • Bakeries
  • Soiled hands not washed due to painful skin
    lesions
  • Contaminated baked goods when applying sugar
    glaze with bare hands
  • Deli shop
  • 76 year old grandmother typhoid carrier handled
    cannelloni without gloves after they were cooked
    once a week

77
Data Sources
  • Outbreak data from 1927 to 2004 from
  • Michigan (2000-2003) State line listings
  • Minnesota (1999-2004) State line listings and
    outbreak reports
  • New York (1985-2000) State line listings
  • Washington (1990-2003) State line listings and
    outbreak reports
  • Health Canada (1976-1996) Line listings from
    annual reports of foodborne and waterborne
    disease outbreaks
  • Outbreak reports from other countries
  • Published peer-reviewed literature including
    reviews

78
Large Gathering and Shigellosis
  • For 2 weeks, food was prepared in 47 communal
    kitchens in a national forest area for a Rainbow
    gathering in North Carolina in 1987
  • There were no toilets, hand washing facilities,
    safe drinking water sources, or refrigeration
  • The outbreak began on July 4 1987, and rapidly
    spread throughout the gathering until it was
    closed on July 15 with a total of 6350 cases
  • Transmission was assumed to be by food, water,
    and person-to-person contact.
  • Secondary infections occurred after ill persons
    returned to home communities in other parts of
    the US

79
Cake and Norovirus
  • A cake requiring direct hand contact during its
    preparation was associated with the majority of
    illnesses in an outbreak of 2700 persons in 2002
    in Massachusetts
  • At least two bakery employees experienced
    norovirus-compatible illness during the week
    preceding the weddings. Two wedding guests, a
    wedding hall employee, and one of the bakery
    employees were ill identical sequence types were
    detected in the stool specimens submitted

80
Shigellosis from Hamburgers in a Resort
  • A butcher who prepared hamburger patties at a
    resort in Haiti in 1984 had a Shigella flexneri
    infection and continued working while ill during
    the 3-week period in which 1,136 guests reported
    illness
  • Illnesses were linked only to those who consumed
    raw or rare hamburger this was followed by
    secondary person-to-person spread between
    roommates

81
Categorization of Outbreaks Where Food Workers
Were Implicated
  • 1. Single food worker causes an outbreak though
    contamination of food or food contact surfaces
  • 2. Single food worker infects other workers
    (victims) who in turn infect consumers/patrons
    though contamination of food or food contact
    surfaces
  • a) in the same establishment or
  • b) in a separate location

82
Transfer of Organisms from Hands
  • Study using Nalidixic acid-resistant Enterobacter
    aerogenes as a surrogate for an enteric pathogen
    to follow cross-contamination demonstrated that
    after handling chicken, contaminated hands
    transferred 2.4 to 5.7 log10 of bacteria to a
    spigot used to wash hands after washing 1.9 to
    6.5 log10 still remained on hands (Chen et al.
    2001)
  • Perez et al. (2006) showed that there was a high
    risk with the use of the same gloves to handle
    contaminated chicken meat and then slice ham
    compared to the safer use of different gloves to
    handle each product

83
Listeria monocytogenes in Different
Cross-contamination Scenarios (Perez et al., 2006)
  • A series of cross contamination scenarios at
    retail were ranked according to their risk level
  • The highest risk corresponded to the use of the
    same gloves to handle contaminated chicken meat
    and then sliced ham compared to the safer use of
    different gloves to handle each product
  • The lowest risk corresponded to use of gloved
    hands but washed between handling the chicken and
    slicing the ham (only 250/100,000 slices would be
    contaminated)
  • All scenarios were capable of ham reaching levels
    above 108 cfu/g after storage when growth can
    occur
  • Lack of knowledge of transfer rates provided the
    model with an important uncertainty component

84
Simulated Distribution of L. monocytogenes at the
Time of Consumption (N) for 3 Scenarios Perez et
al., 2006)
85
Effective Handwashing                
  • Wash, rinse, dry
  • Fingernail brush
  • Instant hand sanitizer
  • Frequent (Task appropriate)
  • Minimize cross-contamination-use handsfree
    devices, e.g., turn on tap/faucet
  • Paper towel dispensers/hot air drying/doorless
    entry or automatic doors
  • Handwash process monitored, documented and
    verified (MDV)

86
Studies on Handwashing
  • Thumbs, palms, spaces between fingers, and
    fingertips including the fingernail area, are
    areas in which contamination is most likely to
    remain. Hand drying may help make up for
    deficiencies in the washing process
  • E. coli and Pseudomonas fluorescens mixed with
    ground beef and rubbed onto hands were 95
    removed with a single handwashing using an E1
    soap
  • a 75 reduction was subsequently shown with a tap
    water wash only
  • Giardia was removed form the hands with soap and
    handwashing. When 10,000 cysts were placed in
    the palm of the hand, handwashing eliminated 99
    (100 cysts)

87
Studies on Handwashing
  • Based on laboratory testing using artificial
    contaminants, the effectiveness of handwashing,
    including washing, rinsing and drying, ranged
    from 2 to 3 log10 reduction (99-99.9)
  • Compliance rates for handwashing are estimated at
    50 but no surveys have been done

88
Food Preparation and Environmental Control
  • Follow proper cooking, hot holding, chilling and
    storage procedures
  • Environmental controls
  • Disinfect surfaces often
  • Clean change of work clothing

89
Airflight Illnesses
  • 1. British Airways flights in 1984 with a total
    of 866 cases 631 passengers, 135 aircrew, and
    100 catering personnel and loaders, with 2
    passenger deaths
  • An ill chef prepared the aspic glaze, which was
    then left at ambient temperatures
  • Also, it was reported that a party given by a
    senior catering manager at the catering center
    resulted in all guests becoming ill, with two
    hospitalized
  • 2. Charter flights to and from Canary Islands to
    Finland in 1976 resulted in 1,800 salmonellosis
    cases
  • Salmonella Typhimurium phage type 96 was isolated
    from passengers, mayonnaise, and one food worker
    in the Las Palmas catering establishment

90
Airflight Illnesses
  • 1. British Airways flights in 1984 with a total
    of 866 cases 631 passengers, 135 aircrew, and
    100 catering personnel and loaders, with 2
    passenger deaths
  • An ill chef prepared the aspic glaze, which was
    then left at ambient temperatures
  • Also, it was reported that a party given by a
    senior catering manager at the catering center
    resulted in all guests becoming ill, with two
    hospitalized
  • 2. Charter flights to and from Canary Islands to
    Finland in 1976 resulted in 1,800 salmonellosis
    cases
  • Salmonella Typhimurium phage type 96 was isolated
    from passengers, mayonnaise, and one food worker
    in the Las Palmas catering establishment
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