Bacteria and

Foodborne Illness

National Digestive Diseases Information Clearinghouse

National

Institute of

Diabetes and

Digestive 

and Kidney

Diseases

NATIONAL 

INSTITUTES

OF HEALTH

U.S. Department

of Health and

Human Services

What are foodborne

illnesses?

Foodborne illnesses are caused by eating

food or drinking beverages contaminated

with bacteria, parasites, or viruses.  Harmful chemicals can also cause foodborne

illnesses if they have contaminated food

during harvesting or processing.  Foodborne illnesses can cause symptoms that

range from an upset stomach to more

serious symptoms, including diarrhea,

fever, vomiting, abdominal cramps, and

dehydration.  Most foodborne infections

are undiagnosed and unreported, though

the Centers for Disease Control and Prevention estimates that every year about

76 million people in the United States

become ill from pathogens, or diseasecausing substances, in food.  Of these

people, about 5,000 die.

What are the causes of

foodborne illnesses?

Harmful bacteria are the most common

cause of foodborne illnesses.  Some bacteria may be present on foods when you

purchase them.  Raw foods are the most

common source of foodborne illnesses

because they are not sterile; examples

include raw meat and poultry that may have

become contaminated during slaughter.

Seafood may become contaminated during

harvest or through processing.  One in

10,000 eggs may be contaminated with

Salmonella inside the egg shell.  Produce

such as spinach, lettuce, tomatoes, sprouts,

and melons can become contaminated with

Salmonella, Shigella, or Escherichia coli 

(E. coli) O157:H7.  Contamination can

occur during growing, harvesting, processing, storing, shipping, or final preparation.

Sources of produce contamination are

varied as these foods are grown in soil and

can become contaminated during growth

or through processing and distribution.

Contamination may also occur during

food preparation in a restaurant or a

home kitchen.  The most common form

of contamination from handled foods is

the calcivirus, also called the Norwalk­like

virus.

When food is cooked and left out for more

than 2 hours at room temperature, bacteria

can multiply quickly.  Most bacteria grow

undetected because they don’t produce a

bad odor or change the color or texture of

the food.  Freezing food slows or stops

bacteria’s growth but does not destroy the

bacteria.  The microbes can become reactivated when the food is thawed.  Refrigeration also can slow the growth of some

bacteria.  Thorough cooking is needed to

destroy the bacteria.
What are the symptoms of

foodborne illnesses?

In most cases of foodborne illnesses, symptoms resemble intestinal flu and may last a

few hours or even several days.  Symptoms

can range from mild to serious and include 

•	 abdominal cramps

•	 nausea

•	 vomiting

•	 diarrhea, which is sometimes bloody

•	 fever

•	 dehydration

What are the risk factors of

foodborne illnesses?

Some people are at greater risk for bacterial infections because of their age or an

unhealthy immune system.  Young children,

pregnant women and their fetuses, and

older adults are at greatest risk.

What are the complications

of foodborne illnesses?

Some micro­organisms, such as Listeria

monocytogenes and Clostridium botulinum,

cause far more serious symptoms than

vomiting and diarrhea.  They can cause

spontaneous abortion or death.

In some people, especially children,

hemolytic uremic syndrome (HUS) can

result from infection by a particular strain

of bacteria, E. coli O157:H7, and can lead

to kidney failure and death.  HUS is a rare

disorder that affects primarily children

between the ages of 1 and 10 years and is

the leading cause of acute renal failure in

previously healthy children.  A child may

become infected after consuming contaminated food or beverages, such as meat,

especially undercooked ground beef;

unpasteurized juices; contaminated water;

or through contact with an infected person. 

The most common symptoms of HUS

infection are vomiting, abdominal pain,

and diarrhea, which may be bloody.  In 

5 to 10 percent of cases, HUS develops

about 5 to 10 days after the onset of illness.

This disease may last from 1 to 15 days and

is fatal in 3 to 5 percent of cases.  Other

symptoms of HUS include fever, lethargy

or sluggishness, irritability, and paleness

or pallor.  In about half the cases, the

disease progresses until it causes acute

renal failure, which means the kidneys are

unable to remove waste products from

the blood and excrete them into the urine.

A decrease in circulating red blood cells

and blood platelets and reduced blood

flow to organs may lead to multiple organ

failure.  Seizures, heart  failure, inflam ­

mation of the pancreas, and diabetes can

also result.  However, most children

recover completely.

See a doctor right away if you or your child

has any of the following symptoms with

diarrhea: 

•	 High fever—temperature over 101.5°,

measured orally

•	 Blood in the stools

•	 Diarrhea that lasts more than 3 days

•	 Prolonged vomiting that prevents

keeping liquid down and can lead to

dehydration

•	 Signs of severe dehydration, such as

dry mouth, sticky saliva, decreased urination, dizziness, fatigue, sunken eyes,

low blood pressure, or increased heart

rate and breathing rate

•	 Signs of shock, such as weak or rapid

pulse or shallow breathing

•	 Confusion or difficulty reasoning 

2	 Bacteria and Foodborne Illness
How are foodborne illnesses

diagnosed?

Your doctor may be able to diagnose foodborne illnesses from a list of what you’ve

eaten recently and from results of appropriate laboratory tests.  Diagnostic tests for

foodborne illnesses should include examination of the feces.  A sample of the suspected food, if available, can also be tested

for bacterial toxins, viruses, and parasites.

How are foodborne illnesses

treated?

Most cases of foodborne illnesses are mild

and can be treated by increasing fluid

intake, either orally or intravenously,

to replace lost fluids and electrolytes.

People who experience gastrointestinal

or neurologic symptoms should seek

medical attention.

In the most severe situations, such as HUS,

hospitalization may be needed to receive

supportive nutritional and medical therapy.

Maintaining adequate fluid and electrolyte

balance and controlling blood pressure are

important.  Doctors will try to minimize the

impact of reduced kidney function.  Dialysis may be needed until the kidneys can

function normally.  Blood transfusions also

may be needed.

How are foodborne illnesses

prevented?

Most cases of foodborne illnesses can be

prevented through proper cooking or processing of food, which kills bacteria.  In

addition, because bacteria multiply rapidly

between 40°F and 140°F, food must be kept

out of this temperature range.

Follow these tips to prevent harmful bacteria from growing in food: 

•	 Refrigerate foods promptly.  If prepared food stands at room temperature for more than 2 hours, it may not

be safe to eat.  Set your refrigerator at

40°F or lower and your freezer at 0°F.

•	 Cook food to the appropriate internal

temperature—145°F for roasts, steaks,

and chops of beef, veal, and lamb;

160°F for pork, ground veal, and

ground beef; 165°F for ground poultry;

and 180°F for whole poultry.  Use a

meat thermometer to be sure.  Foods

are properly cooked only when they

are heated long enough and at a high

enough temperature to kill the harmful bacteria that cause illnesses. 

•	 Prevent cross­contamination.  Bacteria

can spread from one food product to

another throughout the kitchen and

can get onto cutting boards, knives,

sponges, and countertops.  Keep raw

meat, poultry, seafood, and their juices

away from all ready­to­eat foods.

•	 Handle food properly.  Always wash

your hands for at least 20 seconds with

warm, soapy water before and after

handling raw meat, poultry, fish, shellfish, produce, or eggs.  Wash your

hands after using the bathroom,

changing diapers, or touching animals.  

3	 Bacteria and Foodborne Illness
•	 Wash utensils and surfaces before

and after use with hot, soapy water.

Better still, sanitize them with diluted

bleach—1 teaspoon of bleach to

1 quart of hot water.

•	 Wash sponges and dish towels weekly

in hot water in the washing machine.

•	 Keep cold food cold and hot food hot.

•	 Maintain hot cooked food at 140°F or

higher.

•	 Reheat cooked food to at least 165°F.

•	 Refrigerate or freeze perishables, produce, prepared food, and leftovers

within 2 hours.

•	 Never defrost food on the kitchen

counter.  Use the refrigerator, cold

running water, or the microwave oven.

•	 Never let food marinate at room temperature—refrigerate it.

•	 Divide large amounts of leftovers into

small, shallow containers for quick

cooling in the refrigerator.

•	 Remove the stuffing from poultry and

other meats immediately and refrigerate it in a separate container.

•	 Wash all unpackaged fruits and veg ­

etables, and those packaged and not

marked “pre­washed,” under running

water just before eating, cutting, or

cooking.  Scrub firm produce such as

melons and cucumbers with a clean

produce brush.  Dry all produce with

a paper towel to further reduce any

possible bacteria.

•	 Do not pack the refrigerator.  Cool air

must circulate to keep food safe.

For more information about prevention of

foodborne illnesses, the U.S. Department

of Agriculture provides a fact sheet on safe

food handling.

What is food irradiation?

Food irradiation is the treatment of food

with high energy such as gamma rays,

electron beams, or x rays as a means of

cold pasteurization, which destroys living

bacteria to control foodborne illnesses.

The United States relies exclusively on the

use of gamma rays, which are similar to

ultraviolet light and microwaves and pass

through food leaving no residue.  Food irradiation is approved for wheat, potatoes,

spices, seasonings, pork, poultry, red meats,

whole fresh fruits, and dry or dehydrated

products.  Although irradiation destroys

many bacteria, it does not sterilize food.

Even if you’re using food that has been

irradiated by the manufacturer, you must

continue to take precautions against foodborne illnesses––through proper refrigeration and handling––to safeguard against

any surviving organisms.  If you are traveling with food, make sure perishable items

such as meats are wrapped to prevent leakage.  Be sure to fill the cooler with plenty

of ice and store it in the car, not the trunk.

If any food seems warmer than 40°F,

throw it out.

4	 Bacteria and Foodborne Illness
Links to Other Disorders

Related to Foodborne

Illnesses

Scientists suspect that foodborne pathogens

are linked to chronic disorders and can

even cause permanent tissue or organ

destruction.  Research suggests that when

some people are infected by foodborne

pathogens, the activation of their immune

system can trigger an inappropriate autoimmune response, which means the immune

system attacks the body’s own cells.  In

some people, an autoimmune response

leads to a chronic health condition. 

Chronic disorders that may be triggered by

foodborne pathogens are

• arthritis 

• inflammatory bowel disease

• kidney failure

• Guillain­Barré syndrome

• autoimmune disorders

Further research is needed to explain the

link between these disorders and foodborne

illnesses.

Common Sources of Foodborne Illnesses

Sources of illness: Raw and undercooked meat and poultry

Symptoms: Abdominal pain, diarrhea, nausea, and vomiting

Bacteria: Campylobacter jejuni, E. coli O157:H7, L. monocytogenes, Salmonella

Sources of illness: Raw foods; unpasteurized milk and dairy products, such as soft

cheeses

Symptoms: Nausea, vomiting, fever, abdominal cramps, and diarrhea

Bacteria: L. monocytogenes, Salmonella, Shigella, Staphylococcus aureus, C. jejuni

Sources of illness: Raw and undercooked eggs.  Raw eggs are often used in foods such

as homemade hollandaise sauce, caesar and other salad dressings, tiramisu, homemade

ice cream, homemade mayonnaise, cookie dough, and frostings.

Symptoms: Nausea, vomiting, fever, abdominal cramps, and diarrhea

Bacterium: Salmonella enteriditis

Sources of illness: Raw and undercooked shellfish

Symptoms: Chills, fever, and collapse

Bacteria: Vibrio vulnificus, Vibrio parahaemolyticus

Sources of illness: Improperly canned goods; smoked or salted fish

Symptoms: Double vision, inability to swallow, difficulty speaking, and inability to

breathe.  Seek medical help right away if you experience any of these symptoms.

Bacterium: C. botulinum

Sources of illness: Fresh or minimally processed produce; contaminated water

Symptoms: Bloody diarrhea, nausea, and vomiting

Bacteria: E. coli O157:H7, L. monocytogenes, Salmonella, Shigella, Yersinia

enterocolitica, viruses, and parasites

5 Bacteria and Foodborne Illness
Points to Remember

Foodborne illnesses result from eating food

or drinking beverages that are contaminated with bacteria, viruses, or parasites.

People at greater risk for foodborne illnesses include young children, pregnant

women and their fetuses, older adults, and

people with lowered immunity.

Symptoms usually resemble intestinal flu.

See a doctor immediately if you have more

serious problems or do not seem to be

improving as expected.

Treatment may range from replacement of

lost fluids and electrolytes for mild cases of

foodborne illnesses to hospitalization for

severe conditions such as HUS.

You can prevent foodborne illnesses by

taking the following precautions:

•	 Wash your hands with warm, soapy

water before and after preparing food

and after using the bathroom or

changing diapers.

•	 Keep raw meat, poultry, seafood, and

their juices away from ready­to­eat

foods.

•	 Cook foods properly and at a high

enough temperature to kill harmful

bacteria.

•	 Refrigerate foods within 2 hours or

less after cooking because cold temperatures will help keep harmful bacteria from growing and multiplying.

•	 Clean surfaces well before and after

using them to prepare food.

6 Bacteria and Foodborne Illness
               

          

           

             

             

                 

           

             

         

           

        

            

             

           

   

              

For More Information

American Dietetic Association

120 South Riverside Plaza, Suite 2000

Chicago, IL  60606–6995

Consumer Nutrition Hotline:  

1–800–877–1600

Internet:  www.eatright.org

Center for Food Safety and Applied

Nutrition

5100 Paint Branch Parkway

College Park, MD  20740–3835

Food Information Line:  

1–888–SAFEFOOD (723–3366)

Internet:  www.cfsan.fda.gov

Centers for Disease Control and

Prevention

1600 Clifton Road

Atlanta, GA  30333

Phone:  1–800–311–3435 or 404–639–3534

Internet:  www.cdc.gov

Gateway to Government Food Safety

Information

Internet:  www.foodsafety.gov 

Partnership for Food Safety Education

655 15th Street NW, 7th Floor

Washington, DC  20201

Phone:  202–220–0651

Internet:  www.fightbac.org

U.S. Department of Agriculture

1400 Independence Avenue SW 

Washington, DC  20250 

Meat and Poultry Hotline:  

1–888–674–6854

Internet:  www.usda.gov

U.S. Department of Health and Human

Services

200 Independence Avenue SW

Washington, DC  20201

Phone:  1–877–696–6775 or 202–619–0257

Internet:  www.os.dhhs.gov

U.S. Environmental Protection Agency

Ariel Rios Building

1200 Pennsylvania Avenue NW

Washington, DC  20460

Phone:  202–272–0167

Internet:  www.epa.gov

U.S. Food and Drug Administration

5600 Fishers Lane

Rockville, MD  20857–0001

Phone: 1–888–INFO–FDA (463–6332) 

Internet:  www.fda.gov

You may also find additional information about this

topic by visiting MedlinePlus at www.medlineplus.gov.

This publication may contain information about

medications. When prepared, this publication

included the most current information available.

For updates or for questions about any medications,

contact the U.S. Food and Drug Administration

toll­free at 1–888–INFO–FDA (1–888–463–6332)

or visit www.fda.gov. Consult your doctor for more

information.

The U.S. Government does not endorse or favor any

specific commercial product or company. Trade,

proprietary, or company names appearing in this

document are used only because they are considered

necessary in the context of the information provided.

If a product is not mentioned, the omission does not

mean or imply that the product is unsatisfactory.

7 Bacteria and Foodborne Illness
       

           

           

          

           

       

            

       

              

          

          

     

       

         

         

       

           

          

         

         

       

           

National Digestive Diseases

Information Clearinghouse

2 Information Way
 

Bethesda, MD  20892–3570
 

Phone:  1–800–891–5389
 

Fax:  703–738–4929
 

Email:  nddic@info.niddk.nih.gov
 

Internet:  www.digestive.niddk.nih.gov
 

The National Digestive Diseases Information

Clearinghouse (NDDIC) is a service of the

National Institute of Diabetes and Digestive and

Kidney Diseases (NIDDK). The NIDDK is

part of the National Institutes of Health of

the U.S. Department of Health and Human

Services. Established in 1980, the Clearinghouse provides information about digestive

diseases to people with digestive disorders and

to their families, health care professionals, and

the public. The NDDIC answers inquiries,

develops and distributes publications, and

works closely with professional and patient

organizations and Government agencies to

coordinate resources about digestive diseases.

Publications produced by the Clearinghouse are

carefully reviewed by both NIDDK scientists and

outside experts. This publication was originally

reviewed by Howard Trachtman, M.D., Long

Island Jewish Medical Center; Peter McNally,

M.D., American College of Gastroenterology;

and Howard Sutter, U.S. Food and Drug

Administration.

This publication is not copyrighted.  The

Clearinghouse encourages users of this fact

sheet to duplicate and  distribute as many

copies as desired.

This fact sheet is also available at 

www.digestive.niddk.nih.gov.

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES

National Institutes of Health

NIH Publication No. 07–4730

May 2007