The most common germs that cause food poisoning are:

• Norovirus: Most people who have heard of norovirus likely think of it as an illness that passes from person to person, particularly among children. However, this virus can also spread through contaminated food and water. Contaminated leafy greens (such as lettuce), fresh fruit, and shellfish cause most outbreaks.
• Salmonella: Over 1 million people in the U.S. each year contract salmonella poisoning from food. It causes almost 400 deaths per year. This infection is often the result of consuming contaminated raw meat, poultry, and seafood.
• Clostridium perfringens: This strain of infection also affects about 1 million people in the U.S. each year. It is found most often in foods like beef, poultry, and pre-cooked foods. It can also be found in dried foods. Outbreaks of this bacteria are most frequently in areas where large amounts of food are prepared. This includes cafeterias or catering facilities.
• Campylobacter: Another foodborne illness that affects over 1 million people in the U.S. each year, campylobacter, is most often contracted by eating raw or undercooked poultry, consuming unpasteurized milk or contaminated water, or by touching these products and not washing your hands.
• Staphylococcus aureus: This particular bacteria is quite common and many of us have the bacteria on our skin and in our nose, without any illness. However, if you carry Staphylococcus aureus and you don’t wash your hands thoroughly before handling food, the bacteria could multiply and cause serious illness to others. The products most likely to spread this germ include salads (especially if they have prepared meats, such as ham and chicken), dairy products, and eggs.

The following four germs are not as common, but they cause the most serious illnesses:

• Clostridium botulinum (botulism): Up to 200 people per year in the U.S. develop botulism, less than 50 of them from food. The bacteria live in the soil where the food grows. The bacteria can grow if food is not processed and canned (or bottled) safely. This produces a toxin. Botulism is a particular concern with home canning.
• Listeria: Listeria poisoning, called listeriosis, only affects about 1,600 people in the U.S. each year, but over 250 die from it. Contracting this infection during pregnancy may not cause serious illness, but it can cause serious complications for the fetus. Listeria may be found in prepared meats, unrefrigerated foods (such as meat spreads), unpasteurized cheeses, and raw sprouts.
• Escherichia coli (E. coli). E. coli is an infection that often hits the news when there is an outbreak. The bacteria itself is all around us and most are harmless. However, there are two types that can cause serious illness. You can learn more about E. coli at Sepsis and Intestinal E. Coli Infections.
• Vibrio: Vibrio causes vibriosis, affecting about 80,000 people in the U.S. each year, causing about 100 deaths. It can spread if you have an open wound exposed to contaminated sea water. But it is a foodborne illness as well, caused by consuming raw or undercooked seafood.

We can’t prevent all infections, including food poisoning. But you can reduce your risk by following these tips:

• Cook all meat thoroughly, particularly ground beef or mechanically tenderized meat.
• Don’t eat raw or undercooked eggs
• Don’t reuse cutting boards or utensils after using them for meat products before washing them in hot, soapy water.
• Drink only pasteurized milk and eat pasteurized dairy products.
• Wash all fruits and vegetables thoroughly.
• Wash your hands thoroughly, especially after touching animals and before and after handling food.

To reduce the risk of contracting infections while in countries where the bacteria are more common:

• Drink bottled water and use bottled water to brush your teeth
• Do not eat undercooked foods.
• Do not use ice cubes made with tap water
• Eat fruits that you can peel yourself
• Wash your hands frequently

The most common symptoms of foodborne illnesses are abdominal cramping, diarrhea, nausea and vomiting. If you experience any of these symptoms and they worsen instead of improve, or if you see fresh blood in your stools, contact your doctor immediately or go the the closest emergency department.

Most cases of food poisoning go away on their own, after the microbes have passed through your body. However, while you are sick, it’s important to stay hydrated. Frequent diarrhea and vomiting can cause dehydration.

This page from the National Institute of Diabetes and Digestive and Kidney Diseases explains how to treat food poisoning at home and what a doctor may do if it is serious enough.

See a doctor as soon as possible if any of the symptoms become severe or if you have any of the following:

• Bloody diarrhea
• Diarrhea for three days or more
• Fever that stays above 102 degrees Fahrenheit
• Vomiting without breaks, not able to keep even liquids down
• Signs of dehydrate (little or no urine, no tears, dry mouth, feeling lightheaded or dizzy)