Foodborne Illness:
Protecting Your Patients,
Your Families and Yourself
Edward C. Oldfield, III, MD
VAMDA Annual Conference
September 13, 2014
“Serenely full, the epicure would say,
Fate cannot harm me for I have eaten
today.”
Sydney Smith (1771-1845)
Lady Holland’s Memoir
“Foodborne diseases continue to move newspapers
and bowels around the world.”
-RV Tauxe
Foodborne Illness
3 facts about foodborne illness lectures:
• Always topical; always an outbreak to talk about.
• High level of interest (personal and professional).
• Remember I am only the messenger; Don’t shoot
the messenger.
Foodborne Illness
• 1.5 billion episodes of diarrhea in the world each year
with 3 million deaths in children less than 5 years old.
• 70% of episodes of diarrhea are felt to be related to food
contamination.
• In the U.S., 48 million episodes of foodborne illness with
128,000 hospitalizations and 3,000 deaths are estimated
to occur each year.
• 2010 estimate of cost: $152 billion.
David Satcher, Surgeon General JAMA 2000;283:1817
Reality is Worse than Reports
• Only 5% of persons presenting for care with diarrhea
have stool samples taken; estimated that only 1 in 36
cases is reported.
Carpenter L. Clin Infect Dis 2008;197:1709-12.
• Center for Science in the Public Interest (CSPI)
maintains an outbreak database; but 55-75% of all
outbreaks reported to CDC have no known etiology or
food vehicle and are not included in the database.
Foodborne Disease Pyramid
Reported to Health Department/CDC (reported. 1)
Culture-confirmed case
Lab tests for organism
Specimen obtained
Person seeks care
Person becomes ill
Exposure in the general population (estimated 36)
Foodborne Outbreaks
• 2009-10: >1,500 reported outbreaks with ~30,000 cases.
• Single etiologic agent identified in 64%; norovirus (42%
of outbreaks, 47% of cases) was most common, followed
by Salmonella. (30%).
• Beef (13%), dairy (12%), fish (12%), poultry (11%) were
the most common foods involved.
MMWR 2013;62:41-7.
Foodborne Disease, U.S.
• Salmonella was the leading cause of hospitalizations
(35%), followed by norovirus (26%).
• Salmonella caused the most deaths (28%), followed by
Toxoplasma (24%), Listeria (19%) and norovirus (11%),
58% > 65 y.o.
• Listeria has the highest case fatality ratio: 17%, with
Vibrio second at 6%, and Salmonella at 0.5%.
Foodborne Disease and LTCFs
• Up to 50% of all foodborne outbreaks occur in LTCFs.
• LTCF residents are 4-fold more likely to die from
gastroenteritis than community dwelling.
• For Salmonella, case fatality is 70-fold higher in LTCFs
than other settings.
• 18% of gastroenteritis deaths occur in LTCFs.
Kirk M. Clin Infect Dis 2010;50:397-404.
Diagnosis and Management of
Foodborne Illness
A Primer for Physicians
MMWR 53 (No.RR-4):2004;1-29.
Clues to Etiology of Foodborne Disease
•
•
•
•
•
Time to symptom onset (incubation).
Duration of illness.
Predominant clinical symptoms.
Population involved.
Food type consumed.
Foodborne Illness: Preformed Toxins
Bacillus cereus
• Abrupt onset: 1 - 6 hours
• N/V, 24 hour duration.
• fried rice.
Staphylococcus aureus
• Abrupt onset: 1 - 6 hours
• N/V, 24 - 48 hour duration.
• Potato, egg salad, cream pastries.
Foodborne Illness: Preformed Toxins
Clostridium perfringens 8-16 hour incubation
• severe cramping abdominal pain, diarrhea, nausea
• 24 - 48 hours duration
• meats, gravy, poor temp control (70-140 F), “food
service germ”
Clostridium botulinum 12-72 hour incubation
• vomiting, diarrhea, blurred vision, diplopia, dysphaagia,
descending paralysis.
• home canned foods/low acid content.
Foodborne Illness: Preformed Toxins
Ciguatera: onset 2-6 hours
• reef fish (grouper, red snapper, amberjack, barracuda)
contaminated by toxin from dinoflagellates.
• GI and Neurologic sx
Scombroid: onset minutes-hours.
• spoiled fish (bluefish, tuna, mackerel)
• Histamine reaction: N/V, skin flushing, throbbing HA,
wheezing.
Incubation Period:Viruses/Bacteria
Noroviruses 12 - 48 hour incubation
• N/V/D (diarrhea more common in adults, vomiting in
children).
• duration:12 - 60 hours.
• shellfish, contamination of salads, fruits/vegetables by
infected workers, cruise ships.
•
•
•
•
Salmonella (1 - 3 days)
Shigella (1 - 2 days)
Campylobacter (2 - 5 days)
EHEC (1 - 8 days)
Salmonella
• Estimated 1.4 million annual infections, 168,000
physician visits, 85,000 hospitalizations, 550 deaths.
• But only 40,000 (3%) reported through the passive
National Salmonella Surveillance System.
• Many vehicles of transmission: produce, eggs, poultry
and other meats, direct animal contact.
Salmonella Foodborne Illness
• Nontyphoidal Salmonella are the second most common
cause of foodborne illness (11%), surpassed only by
Norovirus.
• Salmonella was the leading cause of hospitalizations
(35%), followed by norovirus(26%).
• Salmonella caused the most deaths (28%), but had an
overall low case fatality rate of 0.5%.
Salmonella Nomenclature
• All Salmonella belong to 2 species, S. enterica and S.
bongori with 6 subspecies.
• S. enterica (99% of human infections).
• > 2,000 serovars (serological variants) based on
serotyping of somatic (O) and flagellar (H) antigens;
about 400 in circulation at any time.
• Serovars are named after geographical origin of first
isolate of the new serovar.
• PFGE allows DNA fingerprinting to detect strains within
serotypes to reveal epidemiologic clustering.
Recent Salmonella Outbreaks
• 2013: 430 reported cases of Salmonella Heidelberg
infection from March 2013- Jan. 2014 with 42%
hospitalized, 14% bacteremic in 25 states, 73% of cases
from California.
• Salmonella were resistant to ampicillin, chloramphenicol,
sulfa and tetracycline.
• Traced to 3 lots of Foster Farms brand chicken, 2012
outbreak with 314 cases in 13 states also traced to Foster
Farms.
USDA Impotence
• Foster Farms did not issue a recall of the 3 known
contaminated lots.
• USDA does not have mandatory recall authority.
• USDA can detain adulterated food and have it seized
through the courts, but Salmonella has never been
considered by the FDA as an adulterant, despite causing
> 1 million foodborne infections a year.
• Costco recalled rotisserie chickens (USDA does not
allow Salmonella on ready-to-eat food).
USDA Legally Challenged
• In 1974, APHA sued the Secretary of Agriculture
because it did not warn consumers about Salmonella.
• USDA lawyers claimed that bacteria were so wide spread
in the environment that they could not be considered an
adulterant.
• To this day, USDA considers Salmonella on raw poultry
a natural organism.
• Contamination is allowed as long as the processor
removes it somehow, by washing or antibacterial
treatments.
• Denmark and Sweden have a zero-tolerance policy.
Chicken
• 42 million pounds/day of fresh chicken products in retail
markets.
• Most consumed meat in U.S., 83 pounds
consumed/person in 2013.
• 11% raw chicken breasts (+) for Salmonella, 79%
resistant to at least one antibiotic, 45% had at least 3
class resistance, 27% had at least 5 class resistance.
Antibiotics as Growth Promoters
• 84% of all antibiotics in the U.S are used in agriculture;
70% are given to healthy animals as growth promoters,
as much as 29 million pounds.
• All 27 European Union nations have banned antibiotics
as growth promoters.
• Between 1992 and 2008, Danish farmers increased swine
production 47% while reducing antibiotics by 50%.
28
Campylobacter
• 2 million cases of Campylobacter enteritis each year in
the U.S.
• Up to 88% of broiler chicken carcasses are colonized
with Campylobacter.
• Infectious dose of Campylobacter is only 500 organisms,
an amount easily present in one drop of raw chicken
juice.
Quinolone Resistant Campylobacter
• Quinolone resistant Campylobacter infections increased
from 1.3% in 1992 to 10.2% in 1993.
• Ciprofloxacin resistant Campylobacter was found in 14%
of chicken products in retail markets.
• Molecular subtyping showed a link between resistant
Campylobacter in human infections and domestic
chicken products.
Smith KE. NEJM 1999;350:1525-32.
FDA and Antibiotic Growth Promoters
• FDA made first steps to limit antibiotics as growth
promoters in 1977.
• In a 2012 article in the Atlantic, the author noted that the
FDA “has mastered the art of making inaction look like
action.”
Francis Beinecke. “The Failure of the FDA”
31
Antibiotics in Animal Feed
• 12/2013: FDA announced it will ask pharmaceutical
companies to voluntarily stop labeling antibiotics
important for human infection as acceptable for growth
promotion in animals.
• Antibiotics would require an Rx for animal illness
• If it was mandatory, would require a regulatory process
that would take years.
• Two largest companies, Zoetis and Elanco, have given
signals that they will comply.
32
Good News from Perdue
• Perdue hatchery in Salisbury, Md. receives 1 million
eggs a week, each egg was robotically vaccinated against
a common chicken virus and gentamicin to prevent
infection, even for organic.
• By improving sanitary practices, they announced the
gentamicin has been eliminated from all 15 hatcheries.
• Feed antibiotics have been shifted to ionophores, only
sick chickens receive antibiotics in their water (<5%).
33
“Health” Food Outbreaks
• According to Center for Science in the Public Interest
(CSPI), sprouts are the 9th riskiest food with 31 outbreaks
and 2,000 reported cases from 1990-2009.
• In California in the 1990s, more than 50% of Salmonella
and E. coli 0157:H7 outbreaks where a food vehicle was
confirmed were due to sprouts.
• Banned from California schools in 2001.
• Salmonella species can survive for months under dry
seed storage conditions and increases 3-5 orders of
magnitude during sprouting.
E. coli 0104:H4
• 2011 outbreak from raw sprouts traced to an organic
farm in northern Germany.
• Single lot of fenugreek seeds from Egypt was the likely
source .
• 3,910 reported cases with 782 cases of HUS and 54
deaths; 88% adults (median 42 yo), 68% women.
Frank C. NEJM 2011;365;1771-80.
Alfalfa Sprouts and Salmonella
• Alfalfa spout outbreaks have a preponderance of adult
cases (esp. women, 65-95%).
• Longer incubation period.
• Low recall of ingestion (cross contamination on salad
bars?).
• UTIs (5-50% of isolates from urine).
Can You Rinse Off E.coli 0157:H7?
• Sprouts grown in contaminated water had an increase in
bacterial counts of 100,000 times early in plant growth.
• Mercury chloride disinfectant eliminated E.coli from the
outer surface within 10 minutes.
• Half of the surface disinfected sprouts grew E.coli
0157:H7 when sliced.
• The inner surface of the sprouts were colonized.
Sprouts: The “Un” Health Food
“As currently produced, raw sprouts are an
inherently dangerous food.”
Mohle-Boetani J. Ann Int Med 2001;135:239-47.
Salmonella Serotype Enteritidis (SE) and Eggs
• Average US egg consumption: 258 eggs/person or
65 billion/year.
• According to the CSPI, eggs are the 2nd riskiest food
with 352 outbreaks with 11,000 reported cases from
1990-2009.
• Estimated that only 1 in 38 infections are reported:
true estimate is 400,000 annual SE infections.
• 82% of the outbreaks were associated with raw or
undercooked shell eggs.
Salmonella and Eggs
• Hens have ovarian infections which contaminate the egg
interior, esp the yolk, difficult to eliminate because of the
contaminated environments in chicken production
facilities.
• Current estimate is that 1 in 20,000 eggs are infected in
the U.S. or 2.2 million infected eggs consumed each year
• Most notorious outbreak resulted in estimated 225,000
cases from shipping ice cream in tanker trailer trucks
previously used to transport raw, unpasteurized eggs.
Hennessey T. NEJM 1996;334:1281-6.
Salmonella and Eggs, 2010
• Outbreak with 1,519 cases of Salmonella Enteritidis with
the same PFGE pattern (JEGX01.0004) was identified in
July 2010.
• Traced to Hillandale and Wright County Egg in Iowa,
over 550 million eggs were recalled.
• Egg Safety Rules now require routine testing for SE for
all producers with 50,000 hens and egg refrigeration
within 3 days of laying (previously only when packaged
for the consumer).
Safe Egg Practices
• No one should eat food containing raw eggs: such as
shakes with raw eggs, Caesar salad, Hollandaise sauce,
homemade mayonnaise, ice cream or egg nog.
• Take special care with lightly cooked eggs in omelets,
French toast, lasagna and meringue pies.
Safe Egg Practices
• Eggs should be cooked until the whites and yolks are
firm.
• Salmonella can consistently be isolated from
experimentally contaminated eggs from fried sunny side
up, over easy, soft scrambled or boiled less than 8
minutes.
• Eggs should not be held at room temp and hard boiled
eggs should be refrigerated within 2 hours.
Raw Milk and Disease
• In the 1930s, raw milk was associated with 25% of all
food related outbreaks, fell to 1% with universal
pasteurization.
• Unpasteurized products account for 30% of all dairy
product outbreaks; 70% of milk related outbreaks; 148
from 1998-2011 with 248 hospitalizations.
• Common source of Salmonella Dublin infections,
E coli 0157:H7, Yersinia, Listeria, Tuberculosis,
Brucella, Cryptosporidia, Q fever.
LeJeune J. Clin Infect Dis 2009;48:93-100.
Raw Milk Returns
• Raw milk movement involves 100,000s of people who
consume raw milk as “health food,” 1-3% in U.S.
• FDA banned interstate sales in 1987; illegal in 15 states,
but can be bought in 29 states and sold in retail markets
in 13 states.
• 20-fold more cases reported in states that allow raw milk.
• 2013 AAP policy statement endorsed a ban on the sale of
raw or unpasteurized milk products, including cheeses.
Raw Milk Returns
• 2013 Campylobacter outbreak traced to the same
Pennsylvania dairy that had an outbreak with 148
reported cases in 2012 (est. 4,500 cases).
• From 2005-13, 17 Salmonella and Campylobacter
outbreaks traced to raw milk in Pennsylvania alone.
MMWR 2013;62:702.
• Estimated 150-fold increased risk of foodborne illness
compared with pasteurized milk.
Raw Milk Returns
• In Virginia, you can buy shares in a cow with raw milk
as your return on your investment.
• Wisconsin outlawed “cow sharing” in 2001 after 75
people developed Campylobacter infections.
• Sold by clandestine milk clubs and legally shipped
interstate as “pet food.”
• Nutrition advocacy groups (Westin A. Price Foundation)
list sources at realmilk.com.
• 40 bills to allow raw milk sales have been introduced in
23 states.
E. coli O157:H7
Escherichia coli 0157:H7
• First detected in 1982 from cases of hemorrhagic colitis
associated with hamburger consumption at fast food
restaurants.
• Developed their pathogenic potential 30 years ago with
acquisition of a bacteriophage that carried two shiga like
toxins (SLT’s).
• Name derived from agglutination with antisera to the
somatic or O antigen 157 and the flagellar or H antigen 7.
E.coli 0157:H7 Epidemiology
• 20,000 annual cases of hemorrhagic colitis and 250
deaths. In many series, is more common than Shigella.
• 6-10% of children will develop Hemolytic Uremic
Syndrome (HUS), 50% will require dialysis, now the
leading cause of acute renal failure in children.
• Also responsible for many cases of Thrombotic
Thrombocytopenic Purpura (TTP) in adults.
E.coli 0157:H7 Epidemiology
• Low inoculum will cause infection, similar to Shigella,
with an infective dose of about 100 organisms.
• Leads to person-to-person transmission, especially in day
care facilities.
• Allows contamination of recreational water.
• Susceptibility to chlorine is normal.
E.coli 0157:H7 Clinical
• More than 90% of cases have bloody diarrhea.
• In some series, 20-30% of all person with bloody
diarrhea have E.coli 0157:H7 infections.
• Average case begins with non-bloody diarrhea for one to
two days, then a marked increase in abdominal pain with
the onset of bloody diarrhea which usually prompts the
provider visit.
• Abdominal pain is prominent and can cause confusion
with ischemic colitis.
E.coli 0157:H7 Clinical
• Patients usually afebrile or have only a low grade
temperature and are only moderately dehydrated.
• Duration of illness is usually 4-6 days.
• If HUS is going to occur, it usually begins about one
week after the onset of diarrhea with pallor, oliguria or
anuria and edema.
HUS Risk Factors: Adults
Fever
Age > 65
Antibiotics
WBC > 20K
OR
2.7
3.6
4.7
8.3
Dundas S. Clin Infect Dis 2001;33:923-31.
Detection of Shiga Toxins
• An EIA has been developed to detect Shiga toxinproducing E.coli (Premier EHEC assay; Meridian Diagnostics).
• The EIA test had a 100% sensitivity and a 97%
specificity compared to 60% and 100%, respectively, for
the Sorbitol-MacConkey culture method.
• The EIA detected an additional 20% Shiga toxinproducing E.coli that were non 0157:H7.
Kehl KS. Jour Clin Micro 1997;35:2051-4.
• Recent estimate is that 20-50% of all STEC infections are
due to non-O157. Johnson K. CID 2006;43:1587-95.
E.coli 0157:H7 and Antibiotics
• Prospective cohort study of 71 children under 10 y.o.
with E.coli 0157:H7 diarrhea.
• 5 of the 10 children who developed Hemolytic Uremic
Syndrome received antibiotics.
• In a mutlivariate analysis, use of antibiotics had a relative
risk of 17.3 fold for development of HUS.
Wong CS. NEJM 2000;342:1930-6 .
• In one study, 62% of patients took an antibiotic and 32%
an antimotility agent; 29% after laboratory confirmation.
Nolson J. CID 2011;52:1130-2.
E.coli 0157:H7 1993 Outbreak
• Severity of the 1993 outbreak led the USDA Food Safety
Inspection Service (FSIS) to declare E.coli 0157:H7 an
adulterant in ground beef.
• Meat and grocers groups sued the USDA.
• Federal judge in Texas sided with the USDA saying
E.coli 0157:H7 was so harmful that the USDA was
correct.
• In 2012, the USDA adopted a zero-tolerance policy for 6
other serotypes.
E.coli 0157:H7 Prevention
• Thorough cooking is the most effective preventive
measure.
• Currently, 25% of Americans cook hamburgers rare or
medium rare.
• Core temperature of meat should reach 160 degrees F to
ensure eradication of the organism, meat should be gray
or brown and the juices clear (not as reliable as 160 F).
• Reliance on meat inspection is not currently possible.
Who Eats Pink Hamburger?
• Decreases with age
(22% < 30, 13% > 60 y.o.)
• Increases with education
(less than grade 12: 12%, college education 24%)
• Increases with income
(<$15,000: 12%, >$50,000: 29%)
Listeria
• Listeria has the highest case fatality ratio of foodborne
infections: 17%.
• ~2,000 annual cases with 450 deaths, mostly sporadic
cases.
• Particularly dangerous for pregnant women, neonates,
> 60 y.o. and immunocompromised.
• Develop invasive infections with bacteremia and
meningitis.
Listeria
• L. monocytogenes was grown from at least one food
specimen from 64% of the refrigerators and 11% of all
food samples of patients with invasive disease.
• Significant match between strains from food and from
patients, especially from ready-to-eat foods (those
intended to be eaten without further cooking, such as cole
slaw or pates).
• More likely to have eaten undercooked hotdogs (12
times) or chicken (20 times).
Pinner R. JAMA 1992;267:2046-50.
Listeriosis and Hot Dogs
• From August 1998 thru January 1999, at least 100 cases
of Listeriosis and 20 deaths due to a rare serotype (4b)
were reported from 22 states.
• Cases were traced to hot dogs (Ball Park franks and deli
meats from Bil Mar Foods, a subsidiary of Sara Lee
Corporation), which recalled 35 million pounds of meat.
MMWR 1999 47:1117-18.
Turkey Deli Meat
• 54 cases of Listeriosis with 8 deaths, 3 pregnant women
had fetal deaths in multistate outbreak in 2002 traced to
turkey deli meat. Gottlieb S. Clin Infect Dis 2006;42:29-36.
• Led to recall of 30 million pound of products; resulted in
new FDA testing program for ready-to-eat meat.
• Listeria grows at refrigerator temperatures in these very
long shelf life foods, 50 reported outbreaks related to hot
dogs and luncheon meats.
• Irradiation not yet FDA approved for use with ready-toeat meat.
Listeria and Canteloupes
• 2011 outbreak traced to canteloupes from Coloradobased Jensen Farms.
• 147 reported infections with 33 deaths, 1 miscarriage
from 28 states.
• 86% were > 60 y.o.
• Deadliest foodborne outbreak in 90 years.
McCollum J. NEJM 2013;369:944-53.
Advice for the Immunocompromised,
Pregnant Women and Older Adults
• Avoid all soft cheeses, including feta, camembert, brie
and blue veined cheeses like Roquefort.
• Cook hot dogs until internal temperatures reach 165°.
Cooking in the microwave is not recommended.
• Hot dogs can be kept unopened 2 weeks, opened one
week in refrigerator.
• Avoid deli meats like salami, bologna, corned beef, and
liverwurst, unless cooked as in a hot corned beef
sandwich.
FDA Consumer Advisory
Problems with Pot Pies
• ConAgra sells 100 million pot pies each year (Banquet).
• 10/07: Outbreak of Salmonellosis related to Banquet Pot
Pies with 181 cases reported from 33 states, estimated
15,000 became ill.
• Pot pies are not “ready-to-eat.”
Pot Pies and Microwaves
• Microwave oven: cook only one product at a time.
• Microwave on high. 1100 watt oven or more 4 to 6
minutes. Do not cook in microwave ovens below 1100
watts as potpie may not cook thoroughly. Conventional
oven preparation is recommended.
• Let stand 3 minutes in microwave to complete cooking.
• Check that pot pie is cooked thoroughly. Internal
temperature needs to reach 165F as measured by a food
thermometer in several spots.
Safe Microwave Cooking
• Salmonella outbreaks from frozen not-ready-to-eat
chicken dinners; E. coli out break from frozen pizzas.
• Microwaves produce short radio waves that penetrate
food about 1 inch, which excite water, fat and sugar
molecules to produce heat.
• Heats food unevenly, should not be used to cook raw
foods, esp. frozen foods.
• Use an instant read food thermometer; should reach 165
F, check in multiple places.
Do You Know Your Wattage?
• Cooking instructions are based upon the power or
wattage of the microwave oven; only 29% know the
wattage of their home and 13% outside the home
microwave. MMWR 2008;57:1277-80.
• Actual output may differ from manufacturers rating and
can deteriorate over time.
• Testing: Heat one cup of ice water on high.
• Boils in < 2 minutes; at least 1,000 watts, 2 ½ minutes is
~800 watts and 3 or more 700 watts or less.
www.microwaveovenfacts.com
Food Irradiation
• Uses gamma rays from cobalt 60 with very short
wavelengths similar to ultraviolet light and microwaves.
• Gamma radiation does not elicit neutrons (the sub-atomic
particles which make substances radioactive);
No radioactivity produced.
• Similar to microwaves most of the energy passes through
the food, the small amount that doesn’t is retained as
heat.
Safety of Irradiated Food
• More than 40 years of multi-species, multi-generational
animal studies have shown no toxic effects from eating
irradiated foods.
• Irradiation produces so little chemical change in foods
that it is difficult to design a test to determine if a food
has been irradiated. Free radicals and other compounds
produced during irradiation are identical to those formed
during cooking.
• Endorsed by CDC, WHO, AMA.
Irradiation of Meat
• Only FDA and USDA approved method known to
eliminate E.coli 0157:H7, and reduce Listeria,
Salmonella, and Campylobacter.
• National Center for Policy Analysis estimated that if half
of the highest risk food was irradiated, foodborne illness
would decline by 900,000 cases and 352 deaths would be
averted.
Oysters and Vibrios
• Consumption of raw oysters has been consistently
associated with non-cholera Vibrio infections, including
V. parahemolyticus and V. vulnificus.
• Rates of invasive Vibrio disease are 80 times higher and
mortality 200 times higher for those with liver disease.
• FDA proposed a ban on gulf oysters from warmer
months unless treated, put on hold due to political
pressure.
• Compared to 2010-12, there was a 32% increase in 2013,
highest rates since tracking began in 1996.
MMWR 2014;63:328-32.
Oysters
• Oysters filter 2 gallons of water/hour, Chesapeake Bay
levels are at 1% of historic levels.
• Most Vibrio infections are associated with oysters
harvested in water with temperatures > 71 F between
March and November, primarily from Gulf of Mexico.
• Increasing outbreaks of V. parahemolyticus
gastroenteritis have been associated with change from a
cold-season oyster harvest to a year-round harvest,
Chesapeake Bay has seen an increase in oyster farming
and summer harvests.
Oysters and Vibrios
• Nationally, there are an estimated 35,000 cases annually.
• California banned the sale of raw gulf oysters (2/3 of all
U.S. oysters) from April 1 – October 31 in 2003 as “too
dangerous.”
• From 2003-2010, there were only 4 V. vulnificus cases
and no deaths in California.
Follow Your Mother’s Advice
Only Eat Oysters in a Month with an
“R”
Actually William Butler (1535-1618) said:
“It is unreasonable and unwholesome in all months that
have not an “r” in their name to eat an oyster.”
Norovirus
• Noroviruses, a genus in the family Caliciviridae.
• Study has been limited because they can not be grown in
culture or in animal model.
• Noroviruses are the most common viral cause of food
and waterborne outbreaks of acute gastroenteritis,
responsible for 30-50% of all outbreaks; 93% of all
nonbacterial outbreaks.
• Estimated 21 million cases annually in the US.
• Large outbreaks in nursing homes, hospitals and cruise
ships, strong winter seasonality
Norovirus Outbreaks
• 4 genogroups, >20 genotypes, undergoes genetic “drift”
and “shift” similar to influenza virus.
• Recent widespread increase in outbreaks with the
emergence of 2 new strains of GII norovirus.
MMWR 2007;56:842-6.
• Median viral load in fecal specimens is > 100-fold higher
with GII as compared to GI strains.
Chan M. Emerg Infect Dis 2006;12;1278-80.
Norovirus: Infectivity
• Shed primarily in stool and vomitus for an average of 4
weeks, with peak shedding 2-5 days after infection with
~100 billion virions in a gram of stool.
• Extremely contagious; infectious dose 18 virions (5
billion infectious doses/gram of stool, world population:
7 billion).
• 30% of infections may be asymptomatic with viral
shedding.
Norovirus Transmission
• Infected food handlers during preparation (70% of
outbreaks), esp. foods eaten raw (leafy vegetables, fruits,
shellfish); responsible for 75% of outbreaks.
• Fecal contamination: oysters from fishermen, raspberries
from fieldhands.
Norovirus Outbreaks
•
•
•
•
•
Nursing homes/hospitals: 35%
Restaurants, parties, events: 31%
Schools/day care centers: 13%
Vacation settings/cruise ships: 21%
Other: 9%
Kaplan’s Criteria
•
•
•
•
Median incubation 24-48 hours.
Median duration 12-60 hours.
>50% with vomiting.
No bacterial agent identified.
Norovirus: Diagnosis
• Diagnostic tests generally not available to practicing
clinician.
• PCR of stool or vomitus is the preferred technique;
Electron microscopy can also be used.
• EIA of acute/convalescent serum specimens, not
recommended for clinical dx in sporadic cases.
• CDC Viral Gastroenteritis Section 404 639 3577
calicinet@cdc.gov
Norovirus: Prevention
• Cruise ship: voluntary isolation in cabin until 24-48
hours after sx have resolved.
• Handwashing with soap and water, efficacy of
alcohol/hand sanitizers: minimal to no activity.
• Surface decontamination: 5.25% sodium hypochlorite
(bleach).
Norovirus: Prevention
• Avoiding bare-hand contact with ready-to-eat foods.
• HCWs and food handlers: exclude from work until 48-72
hours after sx have resolved.
• Paid sick-leave programs.
Norovirus: Prevention
• Observational study of food workers in restaurants found
proper handwashing in only 27% of activities; 16% when
gloves were used. Green L. J Food Prot 2006;69:2417-23.
• 20% admitted to having worked at least one shift in the
last year while ill with vomiting or diarrhea.
Carpenter L. J Food Protect 2013;76:2146-54.
• Training and certification of kitchen managers in
appropriate food safety practices was assoc. with
decreased Norovirus outbreaks.
Hedberg C. J Food Protect 2006;69:2697-702.
Updated Norovirus Outbreak
Management and Disease Prevention
Guidelines
Hall A. MMWR 2011; 60(RR03):1-15.
FDA FSMA
• FDA Food Safety Modernization Act was passed in
January 2011.
• Mandates adoption of control plans and increased
inspections with frequency determined by risk based
standards.
• Development of food tracing systems.
• Provides mandatory recall authority (previously
voluntary for food producer).
FDA FSMA: Problems
• Does not regulate meat, poultry and egg products (USDA
control).
• Cost $1.4 billion over next 5 years, but no additional
funds or fees were approved.
• Concern about lack of funding and enforcement; House
of Representatives cut $87 million from 2012 FDA food
safety budget.
• Small producers are exempt.
Risky Behavior in the Kitchen
CDC survey of 20,000 persons revealed:
• 50% eat undercooked eggs.
• 20% eat pink hamburgers.
• 20% do not wash hands after handling raw meat or
chicken.
• 20% do not wash a cutting board with soap or bleach
after using it to cut raw meat or chicken.
MMWR 1998;47 (No.55-4):33-42.
Clean, Separate, Cook, Chill
• Clean:
Wash hands and surfaces often.
• Separate:
Don’t cross contaminate.
• Cook:
Cook to proper temperature.
• Chill:
Refrigerate promptly.
Clean:Wash hands/surfaces often.
• Wash your hands at least 20 seconds.
• Wash your cutting boards, dishes, utensils and counter
tops with hot soapy water after preparing each food item
and before you go on to the next food.
• Use plastic or non-porous cutting boards.
• Consider paper towels for cleaning surfaces.
Kitchen Sanitation
• 90% of kitchen cloths and 46% of kitchen sinks had
> 100,000 bacteria per cm2
• 15% of sponges and dishcloths grew Salmonella with
high rates of transfer to fingers.
• Neat housekeepers had the highest bacterial counts, using
contaminated sponges all over.
“Post-flush toilet bowl is cleaner than the kitchen
sink. That’s why your dog drinks from it. He
probably looks at you drinking from the kitchen
sink and thinks: Humans. That’s just so gross.”
Chuck Gerba Professor U. of Arizona.
“You could eat your dinner in a U.S. toilet.”
John Oxford Prof of Virology
Making Sponges & Dishcloths Safe
• Soaking sponges or dishcloths in bleach for 5-10
minutes, rinsing and air drying three times/week
decreased bacterial counts by > 99%.
• Spraying cutting boards and counter tops with Clorox
Clean-up (1.84%) and wiping clean after 30 seconds had
similar effects.
Rusin P. J Applied Microbiol 1998;85:819-28.
Making Sponges & Dishcloths Safe
• Sponges soaked in raw wastewater and then microwaved
for 30 seconds at 100% power had complete inactivation
of E. coli.
Park D. J Environ Health 2006;69:17-24.
• Reports of sponges catching fire while being
microwaved; sponges should be treated while damp only.
Separate: Don’t cross contaminate.
• Especially important with raw meat, poultry and
seafood.
• Never place cooked food on a plate that
previously held raw meat, poultry or seafood.
Cook: Cook to proper temperature.
• Use a clean thermometer that measures the internal
temperatures of cooked foods to make sure that meat,
poultry and casseroles are cooked all the way through.
• Cook roasts and steaks to at least 145 degrees F; whole
poultry to 160 degrees F.
• Cook ground beef to at least 160 degrees F.
• Don’t use recipes in which eggs remain raw or partially
cooked.
Chill: Refrigerate promptly.
• Refrigerate or freeze perishables, prepared foods and
leftovers within two hours or sooner.
• The Thaw Law: Never defrost food at room
temperatures. Thaw food in the refrigerator, under cold
running water or in the microwave. Marinate foods in the
refrigerator.
• Divide large amounts of leftovers into small, shallow
containers for quick cooling in the refrigerator.
Rules for Leftovers
2 hours – 2 inches – 4 days
• 2 hours from oven to refrigerator.
• 2 inches thick to cool it quick.
• 4 days in the refrigerator – otherwise freeze it.
“Everything I eat has been proven by
some doctor or other to be a deadly
poison and everything I don’t eat has
proved to be indispensable for life.
But I go marching on.”
George Bernard Shaw
Food Safety Sources
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USDA Meat and Poultry Hotline 1-800-535-4555
FDA Food Information Line 1-888-Safe Food
FDA Food Safety Website www.cfsan.fda.gov
Fight Bac! Web site: www.fightbac.org
Egg Nutrition Center www.enc-online.org
Interstate Shellfish Sanitation Conference
142@ibm.net 1-803-788-7559