These conditions include:

• liver disease, either from excessive alcohol use, viral hepatitis, or other causes
• hemochromatosis, an iron disorder
• diabetes
• stomach problems, including previous stomach surgery and low stomach acid (for example, from antacid use)
• cancer
• immune disorders, including HIV infection
• long-term steroid use, as for asthma and arthritis.

When symptoms are severe, the victim should see a doctor or get emergency help. This is especially important for those who are most vulnerable. For mild cases of foodborne illness, the individual should drink plenty of liquids to replace fluids lost through vomiting and diarrhea.

Prevention tips

The idea that the food on the dinner table can make someone sick may be disturbing, but there are many steps you can take to protect your families and dinner guests. It's just a matter of following basic rules of food safety.

Prevention of foodborne illness starts with your trip to the supermarket.

• Pick up your packaged and canned foods first.
• Don't buy food in cans that are bulging or dented or in jars that are cracked or have loose or bulging lids.
• Don't eat raw shellfish and use only pasteurized milk and cheese and pasteurized or otherwise treated ciders and juices if you have a health problem, especially one that may have impaired your immune system.
• Choose eggs that are refrigerated in the store. Before putting them in your cart, open the carton and make sure that the eggs are clean and none are cracked.
• Select frozen foods and perishables such as meat, poultry or fish last. Always put these products in separate plastic bags so that drippings don't contaminate other foods in your shopping cart.
• Don't buy frozen seafood if the packages are open, torn or crushed on the edges. Avoid packages that are above the frost line in the store's freezer. If the package cover is transparent, look for signs of frost or ice crystals. This could mean that the fish has either been stored for a long time or thawed and refrozen.
• Check for cleanliness at the meat or fish counter and the salad bar. For instance, cooked shrimp lying on the same bed of ice as raw fish could become contaminated.
• When shopping for shellfish, buy from markets that get their supplies from state-approved sources; stay clear of vendors who sell shellfish from roadside stands or the back of a truck. And if you're planning to harvest your own shellfish, heed posted warnings about the safety of the water.
• Take an ice chest along to keep frozen and perishable foods cold if it will take more than an hour to get your groceries home.

Safe Storage

• The first rule of food storage in the home is to refrigerate or freeze perishables right away. The refrigerator temperature should be 40 degrees Fahrenheit (5 degrees Celsius), and the freezer should be zero F (minus 18 C). Check both "fridge" and freezer periodically with a refrigerator/freezer thermometer.
• Poultry and meat heading for the refrigerator may be stored as purchased in the plastic wrap for a day or two. If only part of the meat or poultry is going to be used right away, it can be wrapped loosely for refrigerator storage. Just make sure juices can't escape to contaminate other foods.
• Wrap tightly foods destined for the freezer. Leftovers should be stored in tight containers.
• Store eggs in their carton in the refrigerator itself rather than on the door, where the temperature is warmer.
• Seafood should always be kept in the refrigerator or freezer until preparation time.
• Don't crowd the refrigerator or freezer so tightly that air can't circulate. Check the leftovers in covered dishes and storage bags daily for spoilage. Anything that looks or smells suspicious should be thrown out.
• A sure sign of spoilage is the presence of mold, which can grow even under refrigeration. While not a major health threat, mold can make food unappetizing. Most moldy foods should be thrown out. But you might be able to save molding hard cheeses, salami, and firm fruits and vegetables if you cut out not only the mold but a large area around it. Cutting the larger area around the mold is important because much of the mold growth is below the surface of the food.
• Always check the labels on cans or jars to determine how the contents should be stored. Many items besides fresh meats, vegetables, and dairy products need to be kept cold. For instance, mayonnaise and ketchup should go in the refrigerator after opening. If you've neglected to refrigerate items, it's usually best to throw them out.
• Some precautions will help make sure that foods that can be stored at room temperature remain safe. Potatoes and onions should not be stored under the sink because leakage from the pipes can damage the food. Potatoes don't belong in the refrigerator, either. Store them in a cool, dry place. Don't store foods near household cleaning products and chemicals.
• Check canned goods to see whether any are sticky on the outside. This may indicate a leak. Newly purchased cans that appear to be leaking should be returned to the store, which should notify the FDA.

Keep It Clean

The first cardinal rule of safe food preparation in the home is: Keep everything clean.

The cleanliness rule applies to the areas where food is prepared and, most importantly, to the cook.

• Wash hands with warm water and soap for at least 20 seconds before starting to prepare a meal and after handling raw meat or poultry.
• Cover long hair with a net or scarf, and be sure that any open sores or cuts on the hands are completely covered. If the sore or cut is infected, stay out of the kitchen.
• Keep the work area clean and uncluttered. Wash countertops with a solution of 1 teaspoon of chlorine bleach to 1 quart of water or with a commercial kitchen cleaning agent diluted according to product directions. They're the most effective at getting rid of bacteria.
• Also, be sure to keep dishcloths clean because, when wet, they can harbor bacteria and may promote their growth. Wash dishcloths weekly in hot water in the washing machine.
• Sanitize the kitchen sink drain periodically by pouring down the sink a solution of 1 teaspoon of bleach to 1 quart of water or a commercial kitchen cleaning agent. Food particles get trapped in the drain and disposal and, along with the moistness, create an ideal environment for bacterial growth.
• Use smooth cutting boards made of hard maple or a non-porous material such as plastic and free of cracks and crevices. Avoid boards made of soft, porous materials. Wash cutting boards with hot water and soap, using a scrub brush. Then, sanitize them by washing in an automatic dishwasher or by rinsing with a solution of 1 teaspoon of chlorine bleach to 1 quart of water.
• Always wash and sanitize cutting boards after using them for raw foods, such as seafood or chicken, and before using them for ready-to-eat foods. Consider using one cutting board only for foods that will be cooked, such as raw fish, and another only for ready-to-eat foods, such as bread, fresh fruit, and cooked fish.
• Always use clean utensils and wash them between cutting different foods.
• Wash the lids of canned foods before opening to keep dirt from getting into the food. Also, clean the blade of the can opener after each use. Food processors and meat grinders should be taken apart and cleaned as soon as possible after they are used.
• Do not put cooked meat on an unwashed plate or platter that has held raw meat.
• Wash fresh fruits and vegetables thoroughly, rinsing under running water. Don't use soap or other detergents. If necessary--and appropriate--use a small scrub brush to remove surface dirt.