What is foodborne
disease?
Foodborne disease is caused by consuming contaminated foods or
beverages. Many different disease-causing microbes, or pathogens,
can contaminate foods, so there are many different foodborne infections.
In addition, poisonous chemicals, or other harmful substances
can cause foodborne diseases if they are present in food.
More than 250 different foodborne diseases have been described.
Most of these diseases are infections, caused by a variety of
bacteria, viruses, and parasites that can be foodborne.
Other diseases are poisonings, caused by harmful toxins or chemicals
that have contaminated the food, for example, poisonous mushrooms.
These different diseases have many different symptoms, so there
is no one "syndrome" that is foodborne illness. However,
the microbe or toxin enters the body through the gastrointestinal
tract, and often causes the first symptoms there, so nausea, vomiting,
abdominal cramps and diarrhea are common symptoms in many foodborne
diseases.
Many microbes can spread in more than one way, so we cannot always
know that a disease is foodborne. The distinction matters,
because public health authorities need to know how a particular
disease is spreading to take the appropriate steps to stop it.
For example, Escherichia
coli O157:H7 infections can spread through contaminated
food, contaminated drinking water, contaminated swimming water,
and from toddler to toddler at a day care center. Depending
on which means of spread caused a case, the measures to stop other
cases from occurring could range from removing contaminated food
from stores, chlorinating a swimming pool, or closing a child
day care center.
What are the most common
foodborne diseases?
The most commonly recognized foodborne infections are those caused
by the bacteria Campylobacter,
Salmonella,
and E.
coli O157:H7, and by a group of viruses called calicivirus,
also known as the Norwalk
and Norwalk-like viruses.
Campylobacter
is a bacterial pathogen that causes fever, diarrhea, and abdominal
cramps. It is the most commonly identified bacterial cause
of diarrheal illness in the world. These bacteria live in
the intestines of healthy birds, and most raw poultry meat has
Campylobacter on it. Eating undercooked chicken,
or other food that has been contaminated with juices dripping
from raw chicken is the most frequent source of this infection.
Salmonella
is also a bacterium that is widespread in the intestines of birds,
reptiles and mammals. It can spread to humans via a variety
of different foods of animal origin. The illness it causes,
salmonellosis, typically includes fever, diarrhea and abdominal
cramps. In persons with poor underlying health or weakened
immune systems, it can invade the bloodstream and cause life-threatening
infections.
E.
coli O157:H7 is a bacterial pathogen that has a reservoir
in cattle and other similar animals. Human illness typically
follows consumption of food or water that has been contaminated
with microscopic amounts of cow feces. The illness it causes
is often a severe and bloody diarrhea and painful abdominal cramps,
without much fever. In 3% to 5% of cases, a complication
called hemolytic uremic syndrome (HUS) can occur several weeks
after the initial symptoms. This severe complication includes
temporary anemia, profuse bleeding, and kidney failure.
Calicivirus,
or Norwalk-like virus is an extremely common cause of foodborne
illness, though it is rarely diagnosed, because the laboratory
test is not widely available. It causes an acute gastrointestinal
illness, usually with more vomiting than diarrhea, that resolves
within two days. Unlike many foodborne pathogens that have
animal reservoirs, it is believed that Norwalk-like viruses spread
primarily from one infected person to another. Infected
kitchen workers can contaminate a salad or sandwich as they prepare
it, if they have the virus on their hands. Infected fishermen
have contaminated oysters as they harvested them.
Some common diseases are occasionally foodborne, even though
they are usually transmitted by other routes. These include
infections caused by Shigella,
hepatitis
A, and the parasites Giardia
lamblia and Cryptosporidia.
Even strep throats have been transmitted occasionally through
food.
In addition to disease caused by direct infection, some foodborne
diseases are caused by the presence of a toxin in the food that
was produced by a microbe in the food. For example, the
bacterium Staphylococcus aureus can grow in some foods
and produce a toxin that causes intense vomiting. The rare
but deadly disease botulism occurs when the bacterium Clostridium
botulinum grows and produces a powerful paralytic toxin
in foods. These toxins can produce illness even if the microbes
that produced them are no longer there.
Other toxins and poisonous chemicals can cause foodborne illness.
People can become ill if a pesticide is inadvertently added to
a food, or if naturally poisonous substances are used to prepare
a meal. Every year, people become ill after mistaking poisonous
mushrooms for safe species, or after eating poisonous reef fishes.
Related links:
Surveillance
for Foodborne Disease Outbreaks
Preliminary
FoodNet Data on the Incidence of Foodborne Illnesses
Are the types of
foodborne diseases changing?
The spectrum of foodborne diseases is constantly changing.
A century ago, typhoid
fever, tuberculosis
and cholera
were common foodborne diseases. Improvements
in food safety, such as pasteurization of milk, safe canning,
and disinfection of water supplies have conquered those diseases.
Today other foodborne infections have taken their place, including
some that have only recently been discovered. For example,
in 1996, the parasite Cyclospora
suddenly appeared as a cause of diarrheal illness related to Guatemalan
raspberries. These berries had just started to be grown
commercially in Guatemala, and somehow became contaminated in
the field there with this unusual parasite. In 1998, a new
strain of the bacterium Vibrio
parahemolyticus contaminated oyster beds in Galveston
Bay and caused an epidemic of diarrheal illness in persons eating
the oysters raw. The affected oyster beds were near the shipping
lanes, which suggested that the bacterium arrived in the ballast
water of freighters and tankers coming into the harbor from distant
ports. Newly recognized microbes emerge as public health
problems for several reasons: microbes can easily spread around
the world, new microbes can evolve, the environment and ecology
are changing, food production practices and consumption habits
change, and because better laboratory tests can now identify microbes
that were previously unrecognized.
In the last 15 years, several important diseases of unknown
cause have turned out to be complications of foodborne infections.
For example, we now know that the Guillain-Barre syndrome can
be caused by Campylobacter
infection, and that the most common cause of acute kidney failure
in children, hemolytic uremic syndrome, is caused by infection
with E.
coli O157:H7 and related bacteria. In the future,
other diseases whose origins are currently unknown may turn out
be related to foodborne infections.
Related links:
New, Reemerging,
and Drug-Resistant Infections
Surveillance
for Foodborne Disease Outbreaks
Preliminary
FoodNet Data on the Incidence of Foodborne Illnesses
What happens in the
body after the microbes that produce illness are swallowed?
After they are swallowed, there is a delay, called the
incubation period, before the symptoms of illness begin.
This delay may range from hours to days, depending on the organism,
and on how many of them were swallowed. During the incubation
period, the microbes pass through the stomach into the intestine,
attach to the cells lining the intestinal walls, and begin to
multiply there. Some types of microbes stay in the intestine,
some produce a toxin that is absorbed into the bloodstream, and
some can directly invade the deeper body tissues. The symptoms
produced depend greatly on the type of microbe. Numerous organisms
cause similar symptoms, especially diarrhea, abdominal cramps,
and nausea. There is so much overlap that it is rarely possible
to say which microbe is likely to be causing a given illness unless
laboratory tests are done to identify the microbe, or unless the
illness is part of a recognized outbreak.
How are foodborne
diseases diagnosed?
The infection is usually diagnosed by specific laboratory
tests that identify the causative organism. Bacteria such
as Campylobacter,
Salmonella,
E.
coli O157 are found by culturing stool samples in the
laboratory and identifying the bacteria that grow on the agar
or other culture medium. Parasites can be identified by
examining stools under the microscope. Viruses are more
difficult to identify, as they are too small to see under a light
microscope and are difficult to culture. Viruses are usually
identified by testing stool samples for genetic markers that indicate
a specific virus is present.
Many foodborne infections are not identified by routine laboratory
procedures and require specialized, experimental, and/or expensive
tests that are not generally available. If the diagnosis
is to be made, the patient has to seek medical attention, the
physician must decide to order diagnostic tests, and the laboratory
must use the appropriate procedures. Because many ill persons
to not seek attention, and of those that do, many are not tested,
many cases of foodborne illness go undiagnosed. For example,
CDC estimates that 38 cases of salmonellosis actually occur for
every case that is actually diagnosed and reported to public health
authorities.
Related links:
Surveillance
for Foodborne Disease Outbreaks
Preliminary
FoodNet Data on the Incidence of Foodborne Illnesses
How are foodborne diseases
treated?
There are many different kinds of foodborne diseases and they
may require different treatments, depending on the symptoms they
cause. Illnesses that are primarily diarrhea or vomiting
can lead to dehydration if the person loses more body fluids and
salts (electrolytes) than they take in. Replacing the lost
fluids and electrolytes and keeping up with fluid intake are important.
If diarrhea is severe, oral rehydration solution such as Ceralyte*,
Pedialyte* or Oralyte*, should be drunk to replace the fluid losses
and prevent dehydration. Sports drinks such as Gatorade*
do not replace the losses correctly and should not be used for
the treatment of diarrheal illness. Preparations of bismuth
subsalicylate (e.g., Pepto-Bismol)* can reduce the duration and
severity of simple diarrhea. If diarrhea and cramps
occur, without bloody stools or fever, taking an antidiarrheal
medication may provide symptomatic relief, but these medications
should be avoided if there is high fever or blood in the stools
because they may make the illness worse.
*CDC does not endorse commercial products or services.
When should I consult
my doctor about a diarrheal illness?
A health care provider should be consulted for a diarrheal illness
is accompanied by
- high fever (temperature over 101.5 F, measured orally)
- blood in the stools
- prolonged vomiting that prevents keeping liquids down (which
can lead to dehydration)
- signs of dehydration, including a decrease in urination,
a dry mouth and throat, and feeling dizzy when standing up.
- diarrheal illness that lasts more than 3 days
Do not be surprised if your doctor does not prescribe an antibiotic.
Many diarrheal illnesses are caused by viruses and will improve
in 2 or 3 days without antibiotic therapy. In fact, antibiotics
have no effect on viruses, and using an antibiotic to treat a
viral infection could cause more harm than good It
is often not necessary to take an antibiotic even in the case
of a mild bacterial infection. Other treatments can help
the symptoms, and careful handwashing can prevent the spread of
infection to other people. Overuse of antibiotics is the
principal reason many bacteria are becoming resistant. Resistant
bacteria are no longer killed by the antibiotic. This means
that it is important to use antibiotics only when they are really
needed. Partial treatment can also cause bacteria to become
resistant. If an antibiotic is prescribed, it is important
to take all of the medication as prescribed, and not stop early
just because the symptoms seem to be improving.
Related links:
Antibiotic
resistance
National Antimicrobial
Resistance Monitoring System (NARMS)
How many cases of
foodborne disease are there in the United States?
An estimated 76 million cases of foodborne disease occur each
year in the United States. The great majority of these cases are
mild and cause symptoms for only a day or two. Some cases
are more serious, and CDC estimates that there are 325,000 hospitalizations
and 5,000 deaths related to foodborne diseases each year.
The most severe cases tend to occur in the very old, the very
young, those who have an illness already that reduces their immune
system function, and in healthy people exposed to a very high
dose of an organism.
Related links:
Food-Related
Illness and Death in the United States
Surveillance
for Foodborne Disease Outbreaks
Preliminary
FoodNet Data on the Incidence of Foodborne Illnesses
How do public health
departments track foodborne diseases?
Routine monitoring of important diseases by public health departments
is called disease surveillance. Each state decides which
diseases are to be under surveillance in that state. In
most states, diagnosed cases of salmonellosis, E.
coli O157:H7 and other serious infections are routinely
reported to the health department. The county reports them
to the state health department, which reports them to CDC.
Tens of thousands of cases of these "notifiable conditions"
are reported every year. For example, nearly 35,000 cases
of Salmonella
infection were reported to CDC in 1998. However, most foodborne
infections go undiagnosed and unreported, either because the ill
person does not see a doctor, or the doctor does not make a specific
diagnosis. Also, infections with some microbes are not reportable
in the first place.
To get more information about infections that might be diagnosed
but not reported, CDC developed a special surveillance system
called FoodNet. FoodNet provides the best available
information about specific foodborne infections in the United
States, and summarizes them in an annual report.
In addition to tracking the number of reported cases of
individual infections, states also collect information about foodborne
outbreaks, and report a summary of that information to CDC.
About 400-500 foodborne outbreaks investigated by local and state
health departments are reported each year. This includes
information about many diseases that are not notifiable and thus
are not under individual surveillance, so it provides some useful
general information about foodborne diseases.
Related links:
Surveillance
for Foodborne Disease Outbreaks
Preliminary
FoodNet Data on the Incidence of Foodborne Illnesses
FoodNet -
CDC/USDA/FDA Foodborne Diseases Active Surveillance Network
Reporting
foodborne illness
Council of State and Territorial
Epidemiologists (CSTE)
What are foodborne
disease outbreaks and why do they occur?
An outbreak of foodborne illness occurs when a group of people
consume the same contaminated food and two or more of them come
down with the same illness. It may be a group that ate a
meal together somewhere, or it may be a group of people who do
not know each other at all, but who all happened to buy and eat
the same contaminated item from a grocery store or restaurant.
For an outbreak to occur, something must have happened to contaminate
a batch of food that was eaten by a the group of people.
Often, a combination of events contributes to the outbreak.
A contaminated food may be left out a room temperature for many
hours, allowing the bacteria to multiply to high numbers, and
then be insufficiently cooked to kill the bacteria.
Many outbreaks are local in nature. They are recognized
when a group of people realize that they all became ill after
a common meal, and someone calls the local health department.
This classic local outbreak might follow a catered meal at a reception,
a pot-luck supper, or eating a meal at an understaffed restaurant
on a particularly busy day. However, outbreaks are increasingly
being recognized that are more widespread, that affect persons
in many different places, and that are spread out over several
weeks. For example, a recent outbreak of salmonellosis was
traced to persons eating a breakfast cereal produced at a factory
in Minnesota, and marketed under several different brand names
in many different states. No one county or state had very
many cases and the cases did not know each other. The outbreaks
was recognized because it was caused by an unusual strain of
Salmonella, and because state public health laboratories
that type Salmonella
strains noticed a sudden increase in this one rare strain.
In another recent outbreak, a particular peanut snack food caused
the same illness in Israel, Europe and North America. Again,
this was recognized as an increase in infections caused by a rare
strain of Salmonella.
The vast majority of reported cases of foodborne illness are not
part of recognized outbreaks, but occurs as individual or "sporadic"
cases. It may be that many of these cases are actually part
of unrecognized widespread or diffuse outbreaks. Detecting
and investigating such widespread outbreaks is a major challenge
to our public health system. This is the reason that new
and more sophisticated laboratory methods are being used at CDC
and in state public health department laboratories.
Related links:
Surveillance
for Foodborne Disease Outbreaks
Preliminary
FoodNet Data on the Incidence of Foodborne Illnesses
Reporting
foodborne illness
FoodNet -
CDC/USDA/FDA Foodborne Diseases Active Surveillance Network
PulseNet
- The National Molecular Subtyping Network for Foodborne Disease
Surveillance
Why do public health
officials investigate outbreaks?
A foodborne outbreak is an indication that something needs to
be improved in our food safety system. Public health scientists
investigate outbreaks to control them, and also to learn how similar
outbreaks can be prevented in the future. Just as when a
fire breaks out in a large building or when an airliner crashes,
two activities are critical when an outbreak occurs. First, emergency
action is needed to keep the immediate danger from spreading,
and second, a detailed objective scientific investigation is needed
to learn what went wrong, so that future similar events can be
prevented. Much of what we know about foodborne disease
and its prevention comes from detailed investigation of outbreaks.
This is often how a new pathogen is identified, and this is how
the critical information linking a pathogen to a specific food
and animal reservoir is first gathered. The full investigation
can require a team with multiple talents, including the epidemiologist,
microbiologist, food sanitarian, food scientist, veterinarian,
and factory process engineer.
How are outbreaks
of foodborne disease detected?
The initial clue that an outbreak is occurring can come
in various ways. It may be when a person realizes that
several other people who were all together at an event have become
ill and he or she calls the local health department. It
may be when a physician realizes she has seen more than the usual
number of patients with the same illness. It may be when
a county health department gets an unusually large number of reports
of illness. The hardest outbreaks to detect are those that
are spread over a large geographic area, with only a few cases
in each state. These outbreaks can be detected by combining
surveillance reports at the regional or national level and looking
for increases in infections of a specific type. This is
why state public health laboratories determine the serotype of
Salmonella
bacteria isolated from people. New "DNA fingerprinting"
technologies can make detecting outbreaks easier too. For
example, the new molecular subtyping network, PulseNet,
allows state laboratories and CDC to compare strains of E.
coli O157:H7 and an increasing number of other pathogens
from all across the United States to detect widespread outbreaks.
After an apparent cluster of cases is detected, it is important
to determine whether these cases represent a real increase above
the expected number of cases and whether they really might be
related. Sometimes a cluster of reported cases is caused
by something other than an actual outbreak of illness. For
example, if the person responsible for reporting has just returned
from a vacation and is clearing up a backlog of cases by reporting
them all at once, the sudden surge of reports is just a false
cluster.
Related links:
Reporting
foodborne illness
FoodNet -
CDC/USDA/FDA Foodborne Diseases Active Surveillance Network
PulseNet
- The National Molecular Subtyping Network for Foodborne Disease
Surveillance
Surveillance
for Foodborne Disease Outbreaks
Preliminary
FoodNet Data on the Incidence of Foodborne Illnesses
How is a foodborne
disease outbreak investigated?
Once an outbreak is strongly suspected, an investigation begins.
A search is made for more cases among persons who may have been
exposed. The symptoms and time of onset, and location of
possible cases is determined, and a "case definition" is developed
that describes these typical cases. The outbreak is systematically
described by time, place, and person. A graph is drawn of
the number of people who fell ill on each successive day to show
pictorially when it occurred. A map of where the ill people
live, work, or eat may be helpful to show where it occurred.
Calculating the distribution of cases by age and sex shows who
is affected. If the causative microbe is not known, samples
of stool or blood are collected from ill people and sent to the
public health laboratory to make the diagnosis.
To identify the food or other source of the outbreak, the investigators
first interview a few persons with the most typical cases about
exposures they may have had in the few days before they got sick.
In this way, certain potential exposures may be excluded while
others that are mentioned repeatedly emerge as possibilities.
Combined with other information, such as the likely sources for
the specific microbe involved, these hypotheses are then tested
in a formal epidemiologic investigation. The investigators conduct
systematic interviews about a list of possible exposures with
the ill persons, and with a comparable group people who are not
ill. By comparing how often an exposure is reported by ill
people and by well people, investigators can measure the association
of the exposure with illness. Using probability statistics,
similar to those used to describe coin flips, the probability
of no association is directly calculated.
For example, imagine that an outbreak has occurred after
a catered event. Initial investigation suggested that
Hollandaise sauce was eaten by at least some of the attendees,
so it is on the list of possible hypotheses. Now, we interview
20 persons who attended the affair, 10 of whom became ill and
10 who remained well. Each ill or well person is interviewed
about whether or not they ate the Hollandaise sauce, as well as
various other food items. If half the people ate the sauce,
but the sauce was not associated with the illness, then we would
expect each person to have a 50/50 chance of reporting that they
ate it, regardless of whether they were ill or not.
Suppose, however, that we find that all 10 ill people but none
of the well persons reported eating Hollandaise sauce at the event?
This would be very unlikely to occur by chance alone if eating
the Hollandaise sauce were not somehow related to the risk of
illness. In fact, it would be about as unlikely as getting
heads ten times in a row by flipping a coin (That is 50% multiplied
by itself 10 times over, or a chance of just under 1 in 1000).
So the epidemiologist concludes that eating the Hollandaise sauce
was very likely to be associated with the risk of illness.
Note that the investigator can draw this conclusion even though
there is no Hollandaise sauce left to test in a laboratory.
The association is even stronger if she can show that those who
ate second helpings of Hollandaise were even more likely to become
ill, or that persons who ate leftover Hollandaise sauce that went
home in doggie bags also became ill.
Once a food item is statistically implicated in this manner,
further investigation into its ingredients and preparation, and
microbiologic culture of leftover ingredients or the food itself
(if available) may provide additional information about the nature
of contamination. Perhaps the Hollandaise sauce was made
using raw eggs. The source of the raw eggs can be determined,
and it may even be possible to trace them back to the farm and
show that chickens on the farm are carrying the same strain of
Salmonella
in their ovaries. If so, the eggs from that farm can be
pasteurized to prevent them from causing other outbreaks.
Some might think that the best investigation method would be
just to culture all the leftover foods in the kitchen, and conclude
that the one that is positive is the one that caused the outbreak.
The trouble is that this can be misleading, because it happens
after the fact. What if the Hollandaise sauce is all gone, but
the spoon that was in the sauce got placed in potato salad that
was not served at the function? Now, cultures of the potato
salad yield a pathogen, and the unwary tester might call that
the source of the outbreak, even though the potato salad had nothing
to do with it. This means that laboratory testing without
epidemiologic investigation can lead to the wrong conclusion.
Even without isolating microbes from food, a well-conducted epidemiologic
investigation can guide immediate efforts to control the outbreak.
A strong and consistent statistical association between illness
and a particular food item that explains the distribution of the
outbreak in time, place and person should be acted upon immediately
to stop further illness from occurring.
An outbreak ends when the critical exposure stops. This
may happen because all the contaminated food is eaten or recalled,
because a restaurant is closed or a food processor shuts down
or changes its procedures, or an infected food handler is no longer
infectious or is no longer working with food. An investigation
that clarifies the nature and mechanism of contamination can provide
critical information even if the outbreak is over. Understanding
the contamination event well enough to prevent it can guide the
decision to resume usual operations, and lead to more general
prevention measures that reduce the risk of similar outbreaks
happening elsewhere.
How does food become
contaminated?
We live in a microbial world, and there are many opportunities
for food to become contaminated as it is produced and prepared.
Many foodborne microbes are present in healthy animals (usually
in their intestines) raised for food. Meat and poultry carcasses
can become contaminated during slaughter by contact with small
amounts of intestinal contents. Similarly, fresh fruits
and vegetables can be contaminated if they are washed or irrigated
with water that is contaminated with animal manure or human sewage.
Some types of Salmonella
can infect a hen's ovary so that the internal contents of a normal
looking egg can be contaminated with Salmonella
even before the shell in formed. Oysters and other filter
feeding shellfish can concentrate Vibrio
bacteria that are naturally present in sea water, or other microbes
that are present in human sewage dumped into the sea.
Later in food processing, other foodborne microbes can be introduced
from infected humans who handle the food, or by cross contamination
from some other raw agricultural product. For example, Shigella
bacteria, hepatitis
A virus and Norwalk
virus can be introduced by the unwashed hands of food handlers
who are themselves infected. In the kitchen, microbes can
be transferred from one food to another food by using the same
knife, cutting board or other utensil to prepare both without
washing the surface or utensil in between. A food that is
fully cooked can become recontaminated if it touches other raw
foods or drippings from raw foods that contain pathogens.
The way that food is handled after it is contaminated can also
make a difference in whether or not an outbreak occurs.
Many bacterial microbes need to multiply to a larger number before
enough are present in food to cause disease. Given warm
moist conditions and an ample supply of nutrients, one bacterium
that reproduces by dividing itself every half hour can produce
17 million progeny in 12 hours. As a result, lightly contaminated
food left out overnight can be highly infectious by the next day.
If the food were refrigerated promptly, the bacteria would not
multiply at all. In general, refrigeration or freezing prevents
virtually all bacteria from growing but generally preserves them
in a state of suspended animation. This general rule has
a few surprising exceptions. Two foodborne bacteria, Listeria
monocytogenes and Yersinia
enterocolitica can actually grow at refrigerator temperatures.
High salt, high sugar or high acid levels keep bacteria from growing,
which is why salted meats, jam, and pickled vegetables are traditional
preserved foods.
Microbes are killed by heat. If food is heated to an internal
temperature above 160oF, or 78oC,
for even a few seconds this sufficient to kill parasites, viruses
or bacteria, except for the Clostridium
bacteria, which produce a heat-resistant form called a spore.
Clostridium spores are killed only at temperatures above
boiling. This is why canned foods must be cooked to a high
temperature under pressure as part of the canning process.
The toxins produced by bacteria vary in their sensitivity to
heat. The staphylococcal toxin which causes vomiting
is not inactivated even if it is boiled. Fortunately, the
potent toxin that causes botulism
is completely inactivated by boiling.
What foods are most
associated with foodborne illness?
Raw foods of animal origin are the most likely to be contaminated;
that is, raw meat and poultry, raw eggs, unpasteurized milk, and
raw shellfish. Because filter-feeding shellfish strain microbes
from the sea over many months, they are particularly likely to
be contaminated if there are any pathogens in the seawater.
Foods that mingle the products of many individual animals, such
as bulk raw milk, pooled raw eggs, or ground beef, are particularly
hazardous because a pathogen present in any one of the animals
may contaminate the whole batch. A single hamburger may
contain meat from hundreds of animals. A single restaurant
omelet may contain eggs from hundreds of chickens. A glass
of raw milk may contain milk from hundreds of cows.
A broiler chicken carcass can be exposed to the drippings and
juices of many thousands of other birds that went through the
same cold water tank after slaughter.
Fruits and vegetables consumed raw are a particular concern.
Washing can decrease but not eliminate contamination, so the consumers
can do little to protect themselves. Recently, a number
of outbreak have been traced to fresh fruits and vegetables that
were processed under less than sanitary conditions. These
outbreaks show that the quality of the water used for washing
and chilling the produce after it is harvested is critical.
Using water that is not clean can contaminate many boxes of produce.
Fresh manure used to fertilize vegetables can also contaminate
them. Alfalfa sprouts and other raw sprouts pose a particular
challenge, as the conditions under which they are sprouted are
ideal for growing microbes as well as sprouts, and because they
are eaten without further cooking. That means that a few
bacteria present on the seeds can grow to high numbers of pathogens
on the sprouts. Unpasteurized fruit juice can also
be contaminated if there are pathogens in or on the fruit that
is used to make it.
What can consumers
do to protect themselves from foodborne illness?
A few simple precautions can reduce the risk of foodborne
diseases:
COOK meat, poultry
and eggs thoroughly. Using a thermometer to measure the
internal temperature of meat is a good way to be sure that it
is cooked sufficiently to kill bacteria. For example,
ground beef should be cooked to an internal temperature of 160o
F. Eggs should be cooked until the yolk is firm.
SEPARATE: Don't
cross-contaminate one food with another. Avoid cross-contaminating
foods by washing hands, utensils, and cutting boards after they
have been in contact with raw meat or poultry and before they
touch another food. Put cooked meat on a clean platter,
rather back on one that held the raw meat.
CHILL: Refrigerate
leftovers promptly. Bacteria can grow quickly at room
temperature, so refrigerate leftover foods if they are not going
to be eaten within 4 hours. Large volumes of food will
cool more quickly if they are divided into several shallow containers
for refrigeration.
CLEAN: Wash produce.
Rinse fresh fruits and vegetables in running tap water to remove
visible dirt and grime. Remove and discard the outermost
leaves of a head of lettuce or cabbage. Because bacteria
can grow well on the cut surface of fruit or vegetable, be careful
not to contaminate these foods while slicing them up on the
cutting board, and avoid leaving cut produce at room temperature
for many hours. Don�t be a source of foodborne illness yourself.
Wash your hands with soap and water before preparing food.
Avoid preparing food for others if you yourself have a diarrheal
illness. Changing a baby�s diaper while preparing food
is a bad idea that can easily spread illness.
REPORT:
Report suspected foodborne illnesses to your local health
department. The local public health department
is an important part of the food safety system. Often calls
from concerned citizens are how outbreaks are first detected.
If a public health official contacts you to find our more about
an illness you had, your cooperation is important. In
public health investigations, it can be as important to talk
to healthy people as to ill people. Your cooperation may
be needed even if you are not ill.
Related links:
Fight BAC!(TM) education campaign
Gateway to Government Food
Safety Information
Are some people more
likely to contract a foodborne illness? If so, are there special
precautions they should take?
Some persons at particularly high risk should take more precautions.
- Pregnant women, the elderly, and those weakened immune systems
are at higher risk for severe infections such as Listeria
and should be particularly careful not to consume undercooked
animal products. They should avoid soft French style cheeses,
pates, uncooked hot dogs and sliced deli meats, which have been
sources of Listeria
infections. Persons at high risk should also avoid alfalfa
sprouts and unpasteurized juices.
- A bottle-fed infant is at higher risk for severe infections
with Salmonella
or other bacteria that can grow in a bottle of warm formula
if it is left at room temperature for many hours. Particular
care is needed to be sure the baby�s bottle is cleaned and disinfected
and that leftover milk formula or juice is not held in the bottle
for many hours.
- Persons with liver disease are susceptible to infections
with a rare but dangerous microbe called Vibrio
vulnificus, found in oysters. They should avoid
eating raw oysters.
What can consumers
do when they eat in restaurants?
You can protect yourself first by choosing which restaurant to
patronize. Restaurants are inspected by the local health
department to make sure they are clean and have adequate kitchen
facilities. Find out how restaurants did on their most recent
inspections, and use that score to help guide your choice.
In many jurisdictions, the latest inspection score is posted in
the restaurant. Some restaurants have specifically trained
their staff in principles of food safety. This is also good
to know in deciding which restaurant to patronize.
You can also protect yourself from foodborne disease when ordering
specific foods, just as you would at home. When ordering a hamburger,
ask for it to be cooked to a temperature of 160oF and
send it back if it is still pink in the middle. Before you
order something that is made with many eggs pooled together, such
as scrambled eggs, omelets or French toast, ask the waiter whether
it was made with pasteurized egg, and choose something else if
it was not.
There is only so
much the consumer can do. How can food be made safer in
the first place?
Making food safe in the first place is a major effort, involving
the farm and fishery, the production plant or factory, and many
other points from the farm to the table. Many different
groups in public health, industry, regulatory agencies, and academia
have roles to play in making the food supply less contaminated.
Consumers can promote general food safety with their dollars,
by purchasing foods that have been processed for safety.
For example, milk pasteurization was a major advance in food safety
that was developed 100 years ago. Buying pasteurized milk
rather than raw unpasteurized milk still prevents an enormous
number of foodborne diseases every day. Now juice pasteurization
is a recent important step forward that prevents E.
coli O157:H7 infections and many other diseases.
Consumers can look for and buy pasteurized fruit juices and ciders.
In the future, meat and other foods will be available that has
been treated for safety with irradiation.
These new technologies are likely to be as important a step forward
as the pasteurization of milk.
Foodborne diseases are largely preventable, though there is no
simple one-step prevention measure like a vaccine. Instead,
measures are needed to prevent or limit contamination all the
way from farm to table. A variety of good agricultural and
manufacturing practices can reduce the spread of microbes among
animals and prevent the contamination of foods. Careful
review of the whole food production process can identify the principal
hazards, and the control points where contamination can be prevented,
limited, or eliminated. A formal method for evaluating the
control of risk in foods exists is called the Hazard Analysis
Critical Control Point, or HACCP
system. This was first developed by NASA
to make sure that the food eaten by astronauts was safe.
HACCP safety principles are now being applied to an increasing
spectrum of foods, including meat, poultry, and seafood.
For some particularly risky foods, even the most careful hygiene
and sanitation are insufficient to prevent contamination, and
a definitive microbe-killing step must be included in the process.
For example, early in the century, large botulism
outbreaks occurred when canned foods were cooked insufficiently
to kill the botulism spores. After research was done to
find out exactly how much heat was needed to kill the spores,
the canning industry and the government regulators went to great
lengths to be sure every can was sufficiently cooked. As
a result, botulism related to commercial canned foods has disappeared
in this country. Similarly the introduction of careful pasteurization
of milk eliminated a large number of milk-borne diseases.
This occurred after sanitation in dairies had already reached
a high level. In the future, other foods can be made
much safer by new pasteurizing technologies, such as in-shell
pasteurization of eggs, and irradiation
of ground beef. Just as with milk, these new technologies
should be implemented in addition to good sanitation, not as a
replacement for it.
In the end, it is up to the consumer to demand a safe food supply;
up to industry to produce it; up to researchers to develop better
ways of doing so; and up to government to see that it happens,
to make sure it works and to identify problems still in need of
solutions.
What is CDC doing to
control and prevent foodborne disease?
CDC is part of the U. S. Public Health Service, with a mission
to use the best scientific information to monitor, investigate,
control and prevent public health problems. Using the tools
of epidemiology and laboratory science, CDC provides scientific
assessment of public health threats. CDC works closely with
state health departments
to monitor the frequency of specific diseases and conducts national
surveillance for them. CDC provides expert epidemiologic
and microbiologic consultation to health departments and other
federal agencies on a variety of public health issues, including
foodborne disease, and it stations epidemiologists in state health
departments to help with the surveillance and investigation of
many problems. CDC can also send a team into the field to conduct
emergency field investigations of large or unusual outbreaks,
in collaboration with state public health officials. CDC
researchers develop new methods for identifying, characterizing
and fingerprinting the microbes that cause disease. We translate
laboratory research into practical field methods that can be used
by public health authorities in States and counties.
CDC is not a regulatory agency. Government regulation of
food safety is carried out by the Food
and Drug Administration (FDA) , the U.S.
Department of Agriculture (USDA), the National
Marine Fisheries Service, and other regulatory agencies.
CDC maintains regular contact with the regulatory agencies.
When new public health threats appear, CDC learns what they are
and how they can be controlled through rapid scientific field
and laboratory investigation. CDC shares the results of these
investigations with the states, with the regulatory federal agencies
and with the industries themselves. Although we do not regulate
the safety of food, CDC assesses the effectiveness of current
prevention efforts. We provide independent scientific assessment
of what the problems are, how they can be controlled, and of where
there are gaps in our knowledge.
What are some
unsolved problems in foodborne disease?
As new foodborne problems emerge, several questions need to be
answered before the problem can be successfully controlled.
It takes careful scientific observation and research to answer
these questions. Some pressing unanswered questions include:
- How do the foodborne pathogens spread among the animals themselves,
and how can this be prevented? This includes E.
coli O157:H7 among cattle, Salmonella
Enteritis among egg-laying hens, and Campylobacter
in broiler chickens. If we could prevent the animals
from becoming infected in the first place, we would not have
as much illness in the humans who eat them.
- What is the microbial cause of outbreaks in which no pathogen
can be identified by current methods? This is true for
over half of the reported foodborne outbreaks. Will wider
application of existing experimental diagnostic methods help,
or are these outbreaks caused by pathogens we simply do not
yet know how to identify?
- What would be the impact of basic food safety education of
restaurant workers on the risk of foodborne disease among restaurant
patrons?
- How can the food and water that animals consume be made safer?
- How can we dispose of animal manure usefully, without threatening
the food supply and the environment?
- How can basic food safety principles be most effectively
taught to school children?
- How can we be sure food safety standards in other countries
are as good as those in the United States? As we import
more of our fresh foods from other countries, we need to be
confident that they are produced with the same level of safety
as food in the United States.
- What control strategies in the slaughter plant will reduce
the contamination of poultry meat with Campylobacter?
- How can irradiation
pasteurization of certain high risk foods, such as ground beef,
be used most effectively?
- How do raspberries in Central America get contaminated with
Cyclospora
in the first place? Does this parasite have an animal
reservoir?
- How can alfalfa sprouts and other raw sprouts be produced
safely? Sprouts are unique among foods in that the conditions
for sprouting are also perfect for bacterial growth, and they
are not cooked after that.
Where can I learn more
about food safety and foodborne diseases?
National
Food Safety Initiative
CDC's
Food Safety Initiative home page
U.S. Food and Drug Administration
U.S. Food Safety and Inspection
Service (FSIS)
U.S. Environmental Protection Agency
Role of
the federal agencies in food safety
Gateway to government food
safety information
Partnership for Food Safety
Education/Fight BAC!TM
Food Safety
Training and Education Alliance
Foodborne
Illness Information Center
National
Food Safety Education Month
Travelers' Health
..
|