Each year, 325,000 people are hospitalized with some form of food poisoning of which there are over 250. In all, there are estimated to be 48 million cases of food-borne illness in the United States each year, but most cases never come to the attention of health care professionals, so the actual number is likely to be higher. Because there are so many kinds, experts say, it isn’t always clear even to people who are sick that they have suffered food poisoning. In addition, most cases of food poisoning are isolated incidents. Outbreaks, when two or more people experience similar symptoms after eating food from the same source, are what make the news, but mot cases of food poisoning aren’t outbreaks at all.
There are a number of different pathogens that can cause food poisoning. These include bacteria such as E. coli, salmonella, and campylobacter; chemicals called mycotoxins that are produced by mold and other fungi; parasites, such as nematodes; and viruses, such as hepatitis A and E and norovirus. In addition, viruses called enteroviruses infect bacteria that in turn infest spoiled food. The bacteria themselves may be harmless—though some types of bacteria that are harmful in themselves, such as some species of Clostridum, can also carry enteroviruses—but can infect humans from within their host bacteria even when those bacteria are killed.
So what foods are the biggest dangers? Meat and dairy are often thought of as the biggest sources of food poisoning, but if handled correctly—in particular, if they are cooked thoroughly and kept out of the "danger zone" between 40 and 140 degrees Fahrenheit—these foods are generally fairly safe. Melons and sprouts, however, are difficult to properly clean and are often eaten raw, and so present pathogens with a welcoming environment.
For packaged foods, people often rely on the expiration date as a guide to whether the food in the package is safe, but this is little more than an estimate based on the date of manufacture. Producers do their best to determine when food will spoil, but it’s not an exact science. However, some packaging manufacturers are working on technology that will make it possible for the package itself to indicate whether there are pathogens or mold on the food, providing more detailed information than a printed date.