Nearly any food, but seafood, produce, poultry, beef and eggs are the top five culprits. Raw foods and undercooked meats and seafood, as well as inadequately refrigerated foods, are riskiest, since refrigeration retards the growth of bacteria, and cooking at high temperatures kills most of them. Home-cooked meals are at least as risky as restaurant food.
You’ll probably never know unless you go to a doctor and have a stool test. There are more than 200 foodborne infections, caused by bacteria (notably Salmonella, Staphylococcus, and E.coli), viruses, and parasites. Toxins in the food (such as mushroom toxin) can also cause illness.
It depends on the organism. With some, it can take 100 million organisms; with very virulent ones, a few organisms can cause illness. Viruses generally have a low infectious dose, and multiply much faster than bacteria in the body. Age, gender, ethnicity and general health play a role. People with impaired or underdeveloped immunity (the elderly, young kids, pregnant women) and those with certain diseases (cancer, diabetes or HIV), can become sick from smaller doses and are likely to develop more serious, lasting symptoms and complications.
The incubation period can be anywhere from one hour to several weeks. For the most common infections, it takes four to 48 hours for symptoms to appear. For parasites it can take more than a month. The longer the time lag, the harder it is to figure out the cause. So don’t assume it was your most recent meal made you sick.
No. The microorganisms that cause spoilage are different from those that cause food poisoning, which seldom produce perceptible changes in food. Thus, food that looks and smells okay is just as likely to make you sick as food that looks spoiled.
Actually, there is no such thing as stomach flu; the influenza virus doesn’t cause diarrhea and vomiting. But it may well be an intestinal virus, such as a rotavirus or norovirus. People often call it “food poisoning,” but food may not be involved. The viruses travel in feces: infected people who don't wash hands thoroughly are a common source of outbreaks. You get infected from contaminated food or water or from touching contaminated objects and then touching your mouth or nose. The virus is highly contagious.
Grandma prepared foods in ways that would be thought unsafe today, yet no one got sick. Why is that? In some cases, foods or organisms are different today, according to a report by the Institute of Food Technologists. Foods may contain new organisms, and organisms can evolve to become more virulent. In any case, people back then did get sick, but they usually didn’t know it was food poisoning. Food is much safer today, thanks in large part to better understanding about food handling and preparation, as well as preservatives.
If you have bloody stool, fever, severe abdominal pain or prolonged or severe vomiting or diarrhea, and/or are very dehydrated, you should see a doctor. The elderly, young children, pregnant women and anyone with a weakened immune system should seek medical attention even for milder symptoms.