ISSUED: 3-91
By Fudeko Maruyama, Extension Specialist in Food and Nutrition,
and Joseph O'Leary, Extension Specialist in Food Microbiology.

The most common cause of foodborne illness is improper handling of food, which allows harmful bacteria to grow. Mishandling usually occurs in the home but also can happen in quantity food kitchens or in the food processing plant.
Understanding the nature of foodborne illness-causing bacteria and the common types of foodborne illness helps consumers and food handlers take preventive measures.
In recent years Salmonella has been the leading foodborne illness-causing bacterium. Clostridium, Staphylococcus, Shigella and Campylobacter have also been responsible for many outbreaks. Other bacteria which have been implicated in foodborne illness are Bacillus, Escherichia coli, Listeria, Streptococcus, Vibrio and Yersinia.
These bacteria can cause two types of food illness: food infection and food poisoning. Food infection is caused by eating food containing the living bacteria. Food poisoning is caused by eating foods in which bacteria such as Staphylococcus or Clostridium botulinum have lived and produced a poison, or toxin. The toxin, not the bacteria, causes the illness.

In a recent 5-year period, there were 2,400 outbreaks of foodborne illness in the United States. Bacteria were the cause in 60 percent of the outbreaks where the cause was identified. Those outbreaks involved over 50,000 people and accounted for 92 percent of the cases in confirmed outbreaks. Bacteria were responsible for 96 percent of the 139 fatalities that occurred.
Salmonella accounted for over 50 percent of the outbreaks (342) and cases (31,245) involving bacteria and 30 percent of the fatalities. There were 74 outbreaks involving Clostridium botulinum. Five outbreaks ( 140 cases ) were caused by Listeria monocytogenes and this organism was responsible for 70 deaths. These three bacteria were responsible for 86 percent of all foodborne fatalities.
The average cost per case for medical bills and time lost from work has ranged from $1,500 to $12,500 for most types of foodborne illness. However, the average cost per case for botulism is about $325,000. The total annual cost of all foodborne illnesses may approach $10 billion.

Acute abdominal pain, diarrhea ( can be watery and/or bloody ), dehydration, complete exhaustion, nausea, vomiting and chills are the most common symptoms of foodborne illness. Vomiting is more often seen with food intoxication than with food infection. All symptoms may not be present in all cases.
Onset of symptoms depends on the bacteria and may occur as soon as one to three hours or up to seven days or longer after ingestion.
Duration of the illness is also dependent on the bacteria and can be from about eight hours to 30 days.
Some persons are more susceptible to foodborne illness than others. Infants, the elderly, pregnant women and persons already ill from other causes may be more vulnerable. Also, persons whose immune system is suppressed such as patients undergoing treatment for cancer or recovering from organ transplants should take special precautions to avoid foodborne illness.

Foods Involved
The majority of outbreaks occur because of mishandling of food in the home or in restaurants.
Foods most commonly involved include meat, poultry, fish, eggs, dairy products and raw vegetables. Foods involved with particular illness-causing bacteria are listed below.
Salmonella - poultry, red meats, eggs and dairy products are the most important vehicles of transmission. Cross-contamination has been implicated in many outbreaks. Growth of this pathogen usually occurs in the food when it is not refrigerated properly or cooked adequately. One reason for the increase in salmonellosis is improved food hygiene in processing that has eliminated competing microorganisms that might inhibit Salmonella or cause obvious spoilage such that the food is discarded.
Escherichia coli - foods of animal origin. These foods are often highly contaminated or inadequately cooked or refrigerated which allows for prolific growth.
Clostridium perfringens - in foods, especially meats, prepared ahead of time and leftover foods which are either improperly cooled or not properly reheated.
Staphylococcus aureus - custard and cream-filled bakery goods, ham and poultry have caused the most outbreaks. Most outbreaks are due to inadequate cooling of foods. This bacteria produces a heat-stable toxin which is not inactivated by any amount of cooking.
Clostridium botulinum - in underprocessed home-canned foods and in other foods that are cooked and then held under airtight conditions, such as under a layer of oil or fat. This organism produces a deadly neurotoxin. Fortunately, this toxin is heat sensitive and should be inactivated by bringing food to a boil.
Campylobacter - raw milk and undercooked chicken are the chief foods involved.
Shigella - outbreaks are usually large and tend to involve mass feeding or contaminated water.
Vibrio - raw or improperly cooked fish and seafood.
Listeria - foods implicated include milk, dairy products, eggs, meat, poultry and coleslaw. This bacteria can grow at refrigerator temperatures. Listeria outbreaks are not usually due to mishandling of food in the home.
Yersinia - foods of animal origin, fish and seafood. This organism can also grow at refrigerator temperatures.

Viruses have been identified as the cause of a number of foodborne disease outbreaks in recent years, and it is likely that they are also responsible in many of the instances where no agent has been identified in a foodborne outbreak. Milk and other beverages, shellfish, coleslaw, lettuce and potato salad have been implicated as the carrier in some of the outbreaks.

How to Avoid Foodborne Illness
Don't buy any food in a container that is outdated, broken, bent, leaky or bulging. Many foods now carry freshness dates. Check these dates and purchase the freshest product for good quality and safety.
Avoid dented cans, especially if the seams are dented. Report broken, leaky or bulging cans to the store manager so that the product can be taken off the shelf.
When buying prepared foods, such as in a delicatessen or cafeteria, select carefully. Avoid "problem" foods if they appear to be improperly held. Hot foods should be held above 140 degrees F and cold foods below 40 degrees F. Food may not be safe to eat if held for more than two hours at temperatures between 60 and 125 degrees F the zone where bacteria grow rapidly.
Buy eggs from refrigerated cases. Avoid cracked or dirty eggs as they may be contaminated with Salmonella. Also avoid milk that is not pasteurized.

Home Gardening
Animal and human wastes harbor illness-causing bacteria. Untreated animal wastes used as fertilizer on gardens are hazardous. Likewise, overflow from septic systems can contaminate home-grown produce.

Storing and Holding
Store perishable foods in the refrigerator, or in the freezer for longer storage. When food is cooked the day before or early in the day it is to be eaten, cool it rapidly and place it in the refrigerator so that the food reaches 40 degrees F within two hours.
When ready to use, reheat the foods thoroughly so that the internal temperature reaches 165 degrees F or higher for at least 15 minutes. Bring broths and gravies to a rolling boil for several minutes.
Thaw frozen foods in the refrigerator, not out on the counter at room temperature.

To prevent contamination of food with harmful bacteria during preparation, follow these sanitation rules:
Use hot soapy water to clean cutting board, knives and equipment after they have been used to prepare raw foods.1
Always work with clean hands, washing them with soap after going to the toilet.
Don't use cooking utensils to taste food while cooking or serving. Don't lick your fingers or eat while preparing food.
Keep hands away from mouth, nose and hair. Cover your coughs and sneezes with tissue.
Keep pets away from food, utensils and work surfaces. They are carriers of harmful bacteria.

1 A sanitizing solution, if used, should have 200 parts per million chlorine. Two tablespoons of household chlorine bleach (5.25% sodium hypochlorite) in one gallon water will be the correct strength.
Items to be sanitized should be washed and clean as food particles rapidly weaken the sanitizing power of chlorine Dip utensils for 2 minutes, rinse and dry. In household kitchens, sanitizing solutions are generally unnecessary.

Inadequately cooked meat, poultry and eggs can harbor illness-causing bacteria. Do not eat any raw foods of animal or marine origin. People who already have an underlying health problem are at much greater risk from raw food consumption. This includes milk, meat, eggs, fish and seafood.

To Cook Meat and Poultry In A Microwave Oven
Debone meat before cooking. Bone, which is dense, shields the tissue around it and may keep the shielded area from heating through. Remove large bones from meat before microwaving and cook the deboned portion using the middle-temperature range settings. Slower cooking at lower temperatures ensures more even heating. Rotating meat several times during cooking also helps to ensure even heat penetration.
Carefully observe the cookbook standing time. Where full cooking is vital to kill disease-causing agents in meat and poultry, let the food stand outside the oven (preferably covered with aluminum foil to retain heat) for the full number of minutes recommended to complete cooking.
Test for doneness with a meat thermometer. After the standing time, check meat or poultry in several spots to be sure it has reached the proper internal temperature throughout.

Recommended Cooking Times for Eggs 2
Scrambled 250 degrees F 1 minute
Poached Boiling water 5 minutes
in covered pan
250 degrees F 4 minutes
not covered 250 degrees F 7 minutes
Fried, over-easy 250 degrees F 3 minutes on one side, then turn and 2 minutes on other side
Soft-cooked Boiling water 7 minutes
Meringue 350 degree F oven 3 15-20 minutes
2 American Egg Board, Egg Nutrition Center and USDA-Food Safety and Inspection Service.
3 Microwave ovens are not recommended for cooking meringues because of uneven heating and the possibility for bacteria to survive.

Cooking Meat & Poultry
Meat and poultry cooked throughout to these temperatures are generally safe to eat. For microwave cooking see special instructions.
Temperature (F)
Fresh Beef
140 4
Medium 160
Well Done 170
Ground Beef 170
Fresh Veal 170
Fresh Lamb
Well Done 180
Fresh Pork 170
Turkey 180-185
Boneless Turkey Roast 170-175
Stuffing (inside or outside bird) 165
Cured Pork
Ham, Raw (cook before eating)
Ham, Fully Cooked (heat before serving)  140
Shoulder (cook before eating) 170
Rabbit 180-185
Duck 180-185
Goose 180-185
4 Some illness causing organisms may survive at 140 degrees F.

Know which foods can cause illness and take special care when cooking and serving them. The most perishable foods are those containing meat, poultry, seafood, eggs or milk, hamburger, turkey and chicken salads, deviled eggs, cream pies, and puddings are examples of foods needing special care.
Picnics, pot-luck dinners and group feedings are potential sources of foodborne illness. Keep cold foods below 40 degrees F and hot foods above 140 degrees F. When feeding a crowd, plan for adequate refrigerator space. Rent or borrow chafing dishes or heated servers to keep hot foods hot.
Put leftovers in the refrigerator as soon as you finish eating. Divide large dishes into several small containers so that the food chills rapidly. Leave room for adequate air circulation between containers. Remove chicken or turkey meat from the bones and refrigerate.
Broth and gravy spoil easily. Cool leftovers quickly and put them in the refrigerator. Don't keep them more than one to two days. To serve again, reheat and boil for several minutes; always serve hot.

When canning food at home, follow research-based USDA-Extension Service recommendations and processing times. You can get the most up-to-date food preservation recommendations from your county Extension office.

Risk of food-borne illness can be controlled by proper sanitation practices in the kitchen, correct cooking temperatures and times, and safe food storage conditions which do not allow spoilage organisms to grow. While there are many species of bacteria. viruses, yeasts and molds that can turn a delicious meal into a vehicle for disease, careful emphasis on three broad areas of safe food handling is the most reliable way to reduce possible problems.
Keep it clean. Prevent contamination by keeping raw and cooked foods separate, practicing good personal hygiene and using clean utensils in food preparation.
Keep it hot. Heat potentially hazardous foods rapidly, cook thoroughly, hold above 140 degrees F and reheat foods to 165 degrees F.
Keep it cold. Foods to be refrigerated should be chilled rapidly to 40 degrees F or less. But keep in mind that some bacteria, such as Listeria and Yersinia, can thrive at refrigerator temperatures.

Sources of Information
Frazier, W.C., and D.C. Westhoff. 1988. Food Microbiology (4th Edition). McGraw Hill Book Company, New York
Doyle, M.P. (Ed.). 1989. Foodborne Bacterial Pathogens. Marcel Dekker, Inc., New York
Marriott, N.G. 1989. Principles of Food Sanitation (2nd Edition). Van Nostrand Reinhold, New York
USDA - Food Safety and Inspection Service. Rev. 1988. The Safe Food Book, Your Kitchen Guide.
Institute of Food Technologists. 1988. Bacteria Associated With Foodborne Diseases.