This article first appeared in the St. Louis Beacon, Nov. 2, 2011 - Sarah L. Patrick, an associate professor of epidemiology at St. Louis University School of Public Health, knows the challenges of trying to pinpoint the source of an E. coli outbreak similar to the one that has sickened residents in St. Louis County and surrounding areas. She is former state epidemiologist in Missouri and has worked at the Centers for Disease Control and Prevention.
In spite of the progress that epidemiology has made in identifying potentially life threatening food-borne illnesses, Patrick says the best protection is good hygiene. She stresses the low-tech habits of plenty of hand washing, cleaning counters and others areas where food is left or prepared, and thoroughly cooking food to kill contaminants. Even with these precautions, she says, problems can occur, as when consumers aren't able to cook an item, such as lettuce touched by contaminated hands. In short, she says consumers are still left with a lot of guess work about how best to protect themselves from food-borne illnesses.
"I wish there was a very easy answer to that. Unfortunately, there isn't. Food can smell fine; it can look fine. It can be crisp. But you can't really look at food, most food, and say whether it's contaminated. That's the difficult part."
Her second piece of advice beyond good hygiene is for consumers to keep informed of reports about contaminated food and take no chances when they are in doubt about recalled items.
"It's surprising to me when you have a national recall of food and people will still keep it on their shelves. Remember the case of the salmonella in the peanut butter? Some people could still have a jar. If it's the same label that's being recalled, it's safer just to throw away the jar than possibly getting sick."
On the other hand, experience might tell some consumers that a banned food item isn't going to sicken everyone who consumes it, she admits.
"We've definitely done a number of investigations where you identify a contaminated product where not everybody who eats it gets sick. Whether they had immunity from being exposed before or whether they didn't eat enough of the contaminated product, you really can't tell. So, yes, people can be exposed and not get sick, but the goal is to remove the produce so that nobody gets sick."
She wouldn't say whether she thought food-borne illnesses were more common these days. She points to CDC data showing that many common bugs are preventable. The data show that the incidence of E. coli has dropped 44 percent in about 15 years but that salmonella infections haven't decreased.
Imported food poses some special problems, she says.
"There have been plenty of well-known outbreaks. It may be handled in different ways than our (U.S.) standard practices. It is important to have an idea where our food comes from because it can become contaminated anywhere in the chain. It could be in the handling process. When you're (taking food) a long distance, you're exposing that food to different conditions and more people handling it. That could increase the likelihood of it getting contaminated."
She cited lettuce as an example, but stressed that she wasn't talking in the context of the current E. coli outbreak.
"The contaminant is usually feces," she says. "Sometimes it's directly from animals, but sometimes it's human feces. Lettuce is a good example if it's prepared by handlers who didn't wash their hands thoroughly after going to the bathroom. People might think they have washed perfectly, but they are not necessarily getting it (contaminants) all. That's how the spread can take place."
She says people need to wash for bacteria underneath their fingernails as well as on their hands. She recalled taking part in a food-borne investigation once at a Kansas site where investigators traced the outbreak of bacteria, not E. coli, to one worker's dirty fingernails.
"She dutifully washed her hands and she wasn't trying to do anything wrong. But she had these nice big thick fingernails. We were able to do scrapings and the bacteria that was causing the outbreak was present under her fingernails. She felt really bad about that."
In addition to stressing good hygiene, Patrick says epidemiologists cannot say enough about the value of technology in helping them solve problems. One tool is the "fingerprint" that helps investigators make connections between deadly bugs that might might be found far from the site where the original illness was detected. If investigators can find a sample of the bacteria, it is sent to the CDC where it is compared to fingerprints of other bacteria.
"That's why fingerprinting of the bacteria is so important. Once the information is uploaded, there's software to identify if you're getting more of that bacteria in some places. Rather than having a few cases in one little town, you can connect those cases to those happening somewhere else where people were exposed to the same food."
The downside, Patrick says, is that epidemiologists run into brick walls in spite of thinking they have all the pieces in place to solve the mystery. That happened, she recalled, when taking part in an investigation after many people fell ill following a wedding in South Dakota.
"They were sick after eating a meal at the wedding. (That) is usually a good indication that there was something present in the meal. We did those food histories, interviewed people, took samples from their stools to see if we could grow any organism, grow any bacteria."
Investigators could not identify the illness or its source. It's a mystery that has yet to be solved.
"So sometimes you just don't get the answer even when you have good information about what people ate and drank," Patrick says. "That's frustrating."
Funding for the Beacon's health reporting is provided in part by the Missouri Foundation for Health, a philanthropic organization that aims to improve the health of the people in the communities it serves.
