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James A Butler MD FACP, CAPT MC USN, Chief,
Gastroenterology Service, National Naval Medical Center
Dr Greg Martin, Chief, Infectious Disease Service, National
Naval Medical Center
1. What are foodborne diseases?
Foodborne illnesses are caused by organisms or harmful chemicals
in the food we eat and drink. Most of these illnesses are
caused when certain bacteria, viruses or parasites contaminate
food. Others occur when food is contaminated by harmful chemicals
or toxins. Over 250 different foodborne diseases have been
described. It's not surprising that since most of these infections
or chemicals enter the body through the stomach and intestines,
the most common symptoms are nausea, vomiting, diarrhea and
abdominal discomfort.
2. What are the most common types of
food borne illnesses?
Around a hundred years ago, typhoid fever, tuberculosis and
cholera were some of the most common diseases caused by bacteria
contaminating food and water. Improvements in food processing
and water treatment have almost eliminated these problems
in the United States at the present time. Today, other bacteria
and viruses have become common causes of foodborne disease,
including Campylobacter, Salmonella, E. coli O157:H7, Shigella,
Clostridium botulinium, Hepatitis A and Calciviruses. A bacteria
called Vibrio parahemolyticus, and a parasite called Cyclospora
have been found to be the cause of a few recent outbreaks
of food borne illnesses.
Campylobacter
Campylobacter is the most common bacteria causing food borne
diarrhea in the world. These bacteria live in the intestines
of birds, and can often contaminate raw poultry such as chicken.
Eating undercooked chicken, or eating food contaminated by
juices from raw chicken are common ways of contracting this
illness. Diarrhea that is often bloody, abdominal cramps and
fever are common symptoms. Most people recover from Campylobacter
diarrhea with no special treatment. The illness can also be
treated with antibiotics such as erythromycin, ciprofloxacin
or azithromycin. Rarely, patients can develop arthritis after
an infection with Campylobacter. A small number of people
develop a type of paralysis called Guillain-Barre' syndrome
2-4 weeks after recovering from Campylobacter infection.
Escherichia coli O157:H7
Escherichia coli (E. coli) bacteria are normally found in
everyone's colon, and most types of E coli cause no problems
at all. Certain types of E. coli can however cause serious
illness, most commonly diarrhea. E. coli O157:H7 is a certain
type of E. coli that lives in the intestines of mammals such
as cattle. Humans become ill when they eat food contaminated
by feces of animals infected with this organism. Hamburger
meat seems to be a common source, as the grinding process
allows organisms that were only on the surface of meat to
be mixed throughout. Also, one infected cow can contaminate
a large amount of hamburger as meat from many cattle is often
mixed together. Outbreaks of E. coli O157:H7 have also been
cause by eating contaminated salami, lettuce and alfalfa sprouts,
or drinking unpasteurized milk and apple juice, and contaminated
well water.
E. coli O157:H7 can cause severe and bloody diarrhea with
painful abdominal cramps. Most people recover without problems
in 5 to 10 days. Antibiotics are not particularly helpful.
Less than one in twenty patients, most commonly children,
can develop a severe complication with low blood count, bleeding,
and kidney failure, called hemolytic uremic syndrome.
Enterotoxigenic E. coli is another type of E. coli that can
cause severe watery diarrhea. It is very common in developing
countries, where it's often spread on unwashed fruits and
vegetables, and in drinking water. It is probably responsible
for the majority of traveler's diarrhea, and is very likely
the leading cause of childhood diarrhea in developing countries.
Salmonella
Salmonella is a bacterium found in the intestines of birds,
reptiles and mammals. It can be spread through eating raw
poultry, eggs, meat, and unwashed fruit. A person with this
infection usually develops fever, diarrhea and abdominal cramps.
Most people get better on their own, and do not need medication.
Some sicker patients require antibiotics, intravenous fluids
and hospital admission. In people with weakened immune systems,
salmonella can get into the bloodstream and cause severe illness
and even death. Occasionally, people recovering from salmonella
infection can develop develop irritated eyes, painful joints
and pain with urination, a condition called Reiter's syndrome.
Some people infected with salmonella can have no symptoms
at all, but become chronic carriers who can spread disease
to others. "Typhoid Mary" Mallon, for example, was a cook
in the early 1900's, who was never sick with salmonella, but
had salmonella bacteria in her stool. Over the course of many
years, many people she cooked for became ill, probably from
bacteria passed to food from her hands.
Shigellosis
Shigellosis, also known as bacillary dysentery, is caused
by Shigella bacteria. It is also spread through eating contaminated
food and drink. Persons with this infection develop fever,
bloody diarrhea, and abdominal pain. Although patients can
usually recover without any specific treatment, many patients
are treated with antibiotics once they are diagnosed.
Botulism
Botulism is a disorder caused by a toxic chemical produced
by a bacterium called Clostridium botulinum. This bacteria
grows best in sealed containers such as cans that have not
been heated enough to kill the botulinium spores. The bacteria
grows best where there is little or no oxygen. It produces
a toxin that can cause paralysis, breathing failure, and even
death. Patients ingesting this toxin can develop double vision,
drooping eyelids, slurred speech, difficulty swallowing, and
difficulty breathing.
3. What foods are most likely to carry
illnesses?
Uncooked meat, raw eggs, and unpasteurized milk are the most
likely foods to be contaminated. Foods such as ground beef,
pooled raw eggs or unpasteurized milk, which are prepared
by combining sources from many different animals, are especially
problematic, as a whole batch can be contaminated by one infected
animal. Vegetables that are eaten raw are also a problem,
as they can be contaminated by washing with impure water or
by fertilization with manure from infected animals. Raw shellfish
are easily contaminated by sewage because these animals are
filter feeders that feed by straining large quantities of
seawater.
Even properly prepared food can be cross contaminated when
juices from raw foods are dripped onto cooked food or when
utensils or cutting boards used for raw food are also used
for cooked food.
4. How can we prevent food borne illnesses?
The Centers for Disease Control has a few simple recommendations
for how to decrease the risk of developing a foodborne disease.
- Cook meat, poultry and eggs thoroughly
- Separate cooked and uncooked food. Avoid cross-contamination
by not using platters or utensils contaminated by raw foods
for cooked foods. Put cooked foods on clean platters, not
the ones that held the raw meat.
- Chill leftovers promptly. Don't leave food out for more
than 4 hours
- Clean produce. Wash hands before preparing food and immediately
after handling raw foods.
- Report suspected food borne illness to the local health
department.
WATERBORNE ILLNESS
5. Where does drinking water come from,
and how is it treated?
Drinking water comes from two main sources: groundwater (wells
and springs) and surface water (rivers, lakes, and reservoirs).
Although smaller water utility companies use groundwater sources,
most people in the United States live in big towns and cities,
which get their water from surface water sources.
Water treatment suppliers use different methods to treat
water to make it safe for drinking. Most suppliers use a process
that makes water pass through different steps, including flocculation,
filtration, and disinfection. Flocculation is a process where
chemicals added to the water make dirt and other contaminants
clump together and settle at the bottom. The water is then
passed through filters, which remove smaller particles, and
then disinfected, most commonly with chlorine.
6. Is tap water safe to drink?
Drinking water in the United States is, for the most part,
very safe. Nationwide, over 22 billion dollars a year is spent
operating and maintaining drinking water systems to deliver
clean water to our faucets. The Environmental Protection Agency
(EPA) requires all water companies serving more than 25 people
to test for over a 100 different possible contaminants on
a regular basis.
Bottled water is not necessarily safer than drinking water,
as the same tests and standards recommended by the EPA are
used in preparing bottled water as with tap water. Bottled
water can be useful in times when tap water may become contaminated,
such as during floods or chemical spills.
7. Could my drinking water have contaminants?
No water is absolutely pure. Trace amounts of many different
substances are normally found in drinking water, and are usually
not dangerous unless they occur in abnormally high levels.
Minerals and metals such as selenium, lead and arsenic are
naturally present in water in small amounts, but can also
be present in larger amounts from mining operations. Chemicals
from industrial wastes or pesticides and herbicides from farm
runoff can contaminate drinking water. Harmful parasites and
bacteria from either humans or farm animals can also be washed
into rivers and lakes during heavy rains.
8. What are the organisms and other contaminants
of most concern today?
Cryptosporidium
Cryptosporidium is an organism first noticed as a problem
in the 1980's. It is a parasite that lives in the intestines
of infected animals. It can get into drinking water when heavy
rains wash animal wastes into reservoirs, and it is extremely
resistant to disinfection with chlorine. The symptoms of infection
include stomach cramps and diarrhea. There is no good treatment,
but people with healthy immune systems will recover without
any treatment after approximately 14 days. For patients with
weakened immune systems, such as those infected with HIV,
the disease can be severe, and sometimes can lead to death.
Although there was a major outbreak in Milwaukee in 1993
during which 400,000 people were infected and 40 people died,
"crypto" outbreaks are extremely rare: There have been only
six documented outbreaks in the United States.
Giardia
Giardia is another parasite that usually infects human through
drinking water. It also lives in the intestinal tracts of
animals, and can get into surface water similar to cryptosporidium.
It commonly infects hikers who drink untreated water from
lakes and streams, and is not an uncommon disease in travelers.
Giardia also causes abdominal cramping and diarrhea. Although
most people recover uneventfully in 1 to 2 weeks, it can cause
chronic illness, especially in persons with compromised immune
systems. Fortunately, this infection can be treated with medication.
Like Cryptosporidium, Giardia is resistant to chlorine disinfection.
E. coli and fecal coliforms
E. coli and other similar stool 'coliform' bacteria levels
are often reported in the news. Although these organisms themselves
usually do not cause significant illnesses, they are found
in human feces. When these bacteria are found in water supplies,
they suggest that the water may be contaminated with human
waste.
Arsenic
Arsenic can naturally be found in water in low levels, but
high levels can be caused by contamination from manufacturing
or mining operations. High levels can cause vomiting, abdominal
pain, diarrhea, jaundice and difficulty swallowing. Chronic
exposure to low levels can cause skin cancer, cirrhosis and
liver cancer.
Lead
Lead can leak into drinking water from old pipes, or can
be found in water as a result of mining operations. It can
cause low blood count, mouth ulcers, constipation, and abdominal
pain. In children it can cause delays in physical and mental
development.
Disinfection byproducts
Disinfection byproducts are produced when substances such
as chlorine, which are used to disinfect the water supply,
bind with other chemicals found in water. Although testing
has suggested that very high levels of disinfection byproducts
can cause cancer in laboratory animals, the EPA has been unable
to link the low levels of disinfection byproducts found in
American water supplies to any problems.
9. How do you make sure your tap water
is safe?
The best source of information on your own tap water is your
local water company. Each water supplier is required to publish
a yearly water quality report, which may be found on the web
at http://www.epa.gov/safewater/dwinfo.htm.
If you have your own well, recommendations on how to get your
water tested can be found at http://www.epa.gov/safewater/pwells1.html
The water supplier is supposed to let you know if there are
problems. In emergencies, the supplier may give you recommendations
on how to disinfect your water by boiling it or by adding
small amounts of bleach or iodine.
10. What should you do if you develop
a food borne or water borne illness?
Most persons with food borne or water borne illness recover
spontaneously. Vomiting and diarrhea can lead to dehydration,
so replacing lost fluids and chemicals in the blood are very
important. When the diarrhea or vomiting is severe, it's best
to use oral rehydration fluids such as pedialyte or oralyte,
as juices or even sport drinks such as Gatorade do not have
enough important minerals. Bismuth subsalicylate (Pepto-Bismol)
may help slow down the symptoms. Diarrhea medication such
as loperamide (Imodium) can be used, but if you have a fever
or blood in the stools, this medication can actually make
things worse and should not be used. If you develop fever
over 101.5, dizziness, dry mouth, bloody diarrhea, or if the
diarrhea lasts for more than 3 days, you should see a doctor.
Suspected food or waterborne illnesses should be reported
to your local health department.
11. Bioterrorism and the Gastrointestinal
Tract
The biologic agents thought to most likely be used in a bioterrorism
attack, such as Anthrax, Plague, and Smallpox, would be most
dangerous if spread through the air, and are not likely to
be very effective as a food or water contaminant. These agents
don't usually enter the human body by way of the intestines,
and therefore intestinal symptoms are not often the most important
problems with these diseases. Many of the food or waterborne
illnesses described above could potentially be used to contaminate
our food and water supply. Fortunately, it is not likely that
such attempts would be very likely to cause widespread illness.
There have been attempts to cause illness with foodborne
and waterborne diseases in the past. In 1984, members of the
Rajneeshee cult in Oregon contaminated salad bars in local
restaurants with Salmonella, causing over 700 people to become
ill with nausea, vomiting and diarrhea. In 1996, a hospital
laboratory worker in Texas intentionally contaminated muffins
with Shigella bacteria, and 12 people who ate those muffins
developed bloody diarrhea. Another group, the Aum Shinrikyo
tried to spray botulinum toxin through the streets of Tokyo
in 1990, but failed to cause any harm. There have been quite
a few reports of people trying to contaminate municipal water
supplies with a variety of bacteria, but it appears none of
these were successful, in part because of chlorination in
modern water treatment plants.
12. How should I prepare for a bioterrorism
attack?
In reality, there is little that a person could or should
do to prepare for a bioterrorism attack. Purchasing gas masks,
stockpiling antibiotics at home, or getting immunizations
for bioterrorism agents is not advisable. To quote the American
Medical Association, "The best protection is a strong and
prepared public health system".
Useful Links
Foodborne disease
CDC-Foodborne
Infections
Foodborne
Diseases, NIAID Fact Sheet
www.foodsafety.gov
- Consumer Advice
Waterborne Illness
EPA
Drinking Water and Health: What You Need to Know
American
Water Works Association
Bioterrorism
American
Medical Association
CDC
Bioterrorism FAQ's
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