Frequently Asked
Questions
Salmonella enteritidis
Infection
Egg-associated salmonellosis is an important public health
problem in the United States and several European countries. A
bacterium, Salmonella enteritidis, can be inside perfectly
normal-appearing eggs, and if the eggs are eaten raw or
undercooked, the bacterium can cause illness. During the 1980s,
illness related to contaminated eggs occurred most frequently in
the northeastern United States, but now illness caused by S.
enteritidis is increasing in other parts of the country as
well. Consumers should be aware of the disease and learn how to
minimize the chances of becoming ill.
A person infected with the Salmonella
enteritidis bacterium usually has fever, abdominal cramps, and
diarrhea beginning 12 to 72 hours after consuming a contaminated
food or beverage. The illness usually lasts 4 to 7 days, and most
persons recover without antibiotic treatment. However, the
diarrhea can be severe, and the person may be ill enough to
require hospitalization.
The elderly, infants, and those with impaired immune systems
may have a more severe illness. In these patients, the infection
may spread from the intestines to the blood stream, and then to
other body sites and can cause death unless the person is treated
promptly with antibiotics.

How eggs become contaminated
Unlike eggborne salmonellosis of past decades, the current
epidemic is due to intact and disinfected grade A eggs.
Salmonella enteritidis silently infects the ovaries of
healthy appearing hens and contaminates the eggs before the shells
are formed.
Most types of Salmonella live in the intestinal tracts
of animals and birds and are transmitted to humans by contaminated
foods of animal origin. Stringent procedures for cleaning and
inspecting eggs were implemented in the 1970s and have made
salmonellosis caused by external fecal contamination of egg shells
extremely rare. However, unlike eggborne salmonellosis of past
decades, the current epidemic is due to intact and disinfected
grade A eggs. The reason for this is that Salmonella
enteritidis silently infects the ovaries of healthy appearing
hens and contaminates the eggs before the shells are formed.
Although most infected hens have been found in the northeastern
United States, the infection also occurs in hens in other areas of
the country. In the Northeast, approximately one in 10,000 eggs
may be internally contaminated. In other parts of the United
States, contaminated eggs appear less common. Only a small number
of hens seem to be infected at any given time, and an infected hen
can lay many normal eggs while only occasionally laying an egg
contaminated with the Salmonella bacterium.

Who can be
infected?
The elderly, infants, and persons with impaired immune systems
are at increased risk for serious illness.
Healthy adults and children are at risk for egg-associated
salmonellosis, but the elderly, infants, and persons with impaired
immune systems are at increased risk for serious illness. In these
persons, a relatively small number of Salmonella bacteria
can cause severe illness. Most of the deaths caused by
Salmonella enteritidis have occurred among the elderly
in nursing homes. Egg-containing dishes prepared for any of these
high-risk persons in hospitals, in nursing homes, in restaurants,
or at home should be thoroughly cooked and served promptly.

What is the
risk?
In affected parts of the United States, we estimate that one in
50 average consumers could be exposed to a contaminated egg each
year. If that egg is thoroughly cooked, the Salmonella
organisms will be destroyed and will not make the person sick.
Many dishes made in restaurants or commercial or institutional
kitchens, however, are made from pooled eggs. If 500 eggs are
pooled, one batch in 20 will be contaminated and everyone who eats
eggs from that batch is at risk. A healthy person's risk for
infection by Salmonella enteritidis is low, even in the
northeastern United States, if individually prepared eggs are
properly cooked, or foods are made from pasteurized eggs.

What you can do to reduce risk
Eggs, like meat, poultry, milk, and other foods, are safe when
handled properly. Shell eggs are safest when stored in the
refrigerator, individually and thoroughly cooked, and promptly
consumed. The larger the number of Salmonella present in
the egg, the more likely it is to cause illness. Keeping eggs
adequately refrigerated prevents any Salmonella present in
the eggs from growing to higher numbers, so eggs should be held
refrigerated until they are needed. Cooking reduces the number of
bacteria present in an egg; however, an egg with a runny yolk
still poses a greater risk than a completely cooked egg.
Undercooked egg whites and yolks have been associated with
outbreaks of Salmonella enteritidis infections. Both
should be consumed promptly and not be held in the temperature
range of 40 to 140 for more than 2
hours.
Reducing the risk of Salmonella enteritidis
infection
- Keep eggs refrigerated.
- Discard cracked or dirty eggs.
- Wash hands and cooking utensils with soap and water after
contact with raw eggs.
- Eat eggs promptly after cooking. Do not keep eggs warm for
more than 2hours.
- Refrigerate unused or leftover egg- containing foods.
- Avoid eating raw eggs (as in homemade ice cream or eggnog).
Commercially manufactured ice cream and eggnog are made with
pasteurized eggs and have not been linked with Salmonella
enteritidis infections.
- Avoid restaurant dishes made with raw or undercooked,
unpasteurized eggs. Restaurants should use pasteurized eggs in
any recipe (such as Hollandaise sauce or caesar salad dressing)
that calls for pooling of raw eggs.

What
else is being done?
Government agencies and the egg industry have taken steps to
reduce Salmonella enteritidis outbreaks. These steps
include the difficult task of identifying and removing infected
flocks from the egg supply and increasing quality assurance and
sanitation measures.
The Centers for Disease Control has advised state health
departments, hospitals, and nursing homes of specific measures to
reduce Salmonella enteritidis infection. Some states now
require refrigeration of eggs from the producer to the consumer.
The U.S. Department of Agriculture is testing the breeder flocks
that produce egg-laying chickens to ensure that they are free of
Salmonella enteritidis. Eggs from known infected commercial
flocks will be pasteurized instead of being sold as grade A shell
eggs. The U.S. Food and Drug Administration has issued guidelines
for handling eggs in retail food establishments and will be
monitoring infection in laying hens.
Research by these agencies and the egg industry is addressing
the many unanswered questions about Salmonella enteritidis,
the infections in hens, and contaminated eggs. Informed consumers,
food-service establishments, and public and private organizations
are working together to reduce, and eventually eliminate, disease
caused by this infectious organism.
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