Sam Beattie, a food safety extension specialist and assistant professor of food science and human nutrition at Iowa State University, tells consumers that it's almost impossible to ensure that there will not be any pathogenic microorganisms on any raw agricultural product.
"Cut spinach and other packaged greens by their nature cannot be thermally processed to kill pathogens," he said. "Secondly, chemical inactivation of the pathogens is difficult because of the product. Lastly, control over the animals that overfly, graze, slither, crawl, and are otherwise naturally present in a field is impossible. The outbreak in question could have come from something as simple as deer excrement on or near the leaves of a plant. The actual feces may be washed off by rain, irrigation, or other means, but the contamination has occurred."
"We must face the reality that we live in a microbial ocean," Beattie said. "Microorganisms are literally everywhere, including on and inside of us and most of the food that we eat. Fortunately, most do not make us ill, however there are viruses, bacteria, and parasites that will do so. Bacteria are found in the soil in which the food is grown, in the water that it is irrigated with, in the feces and on the hands of those that harvest and handle it, animals that pass through and over the fields leave their waste, pests that eat it or live on it, containers that hold food during transit to processing, almost everywhere through processing."
Beattie urges consumers to remember that processing simply can't eliminate bacteria in fresh foods.
"Bacteria are tough to kill," he said. "During the growing and processing of pre-cut fruits or bagged leafy vegetables, there are several steps that are designed to reduce or eliminate many of the bacteria, but the processing steps must be mild enough to avoid destruction of the produce. So there may be some residual bacteria present on the food. If the food was contaminated by an illness causing bacteria or virus, like other organisms, they may not be completely eliminated by the processing. It is important to prevent these bacteria from growing."
He considers the entire food supply safe, and reports that pre-packaged foods are as safe as most other fresh foods. But it is important to look at how much handling of the fresh food occurs.
"More hand contact may increase the risk of fecal contamination of the food by the handler," he said. "Indeed, the leading cause of food borne illness is a virus that is transmitted by human stool contamination of the food. Also, temperature abuse of any fresh food will increase the potential for illness causing bacteria to grow. Cold is the key for pre-cut or bagged produce."
The specific strain of E. coli in the latest alert, 0157:H7, has been found in a variety of foods and locations, according to Beattie. He said it is generally associated with fecal contamination of soil, water, food, hands and environment, and in one case the air.
"Importantly, a person ill with O157 can easily contaminate others if proper hygiene is not followed. Hand-washing is critically important in working with ill people," he said.
Beattie reports that this strain of E coli seems to be particularly infectious; only 10 to 100 organisms may be needed to make a person ill. Initial symptoms include abdominal cramps and watery diarrhea. Fever usually does not occur.
"In most healthy adults the illness runs its course in about eight days," he said. "Young children and elderly may have very severe complications that include anemia and kidney failure, fever, and neurological issues. This is why it is so important to feed kids well cooked meats and pasteurized juices."