07/16/2008 - 07:55

Food-borne illness: Attack of the killer tomatoes

Laura H. Kahn

Laura H. Kahn

A general internist who began her career in health care as a registered nurse, Kahn works on the research staff of Princeton University's ...

More

Imagine sitting down at a restaurant and enjoying a delicious meal that includes fresh tomatoes and jalapeno peppers. Then, 12 to 72 hours later, stomach cramps, diarrhea, and a fever develop that can last up to a week--possibly, from those tomatoes and/or jalapeno peppers.

Foodborne outbreaks seem to be occurring more frequently in recent years. For instance, since last April, the United States has experienced its largest foodborne outbreak in a decade, spanning nearly every state and sickening more than 1,000 people.

The assumption that restaurant food is safe depends upon the ability of local health departments to conduct and enforce restaurant inspections."

The bacterial culprit is Salmonella, in this case, an unusual strain called Salmonella Saintpaul, which infected food handlers can spread if they don't wash their hands with soap and water after using the toilet. Other bacteria commonly reported and associated with foodborne infections include Camplyobacter, Listeria, and E. coli O157, all of which are associated with animal reservoirs. For example, Campylobacter lives in the intestines of birds, while E. coli O157 lives in cattle. Contamination is typically through irrigation systems. The Calicivirus, known as Norovirus, also commonly causes foodborne illness, but it's usually spread from person-to-person and the symptoms involve more vomiting than diarrhea.

The U.S. Public Health Service began collecting reports of foodborne outbreaks in 1925 when it started publishing summaries of disease outbreaks--including those attributed to milk. These early efforts contributed to laws such as the Pasteurized Milk Ordinance, which led to a decrease in the incidence of milk-associated disease. Forty years later, the quality of foodborne and waterborne disease outbreak surveillance improved further still after the Centers for Disease Control and Prevention (CDC) began incorporating microbial or chemical contamination into their annual summaries, and federal and state epidemiologists increased their active participation in outbreak investigations. (See "Surveillance for Foodborne-Disease Outbreaks--United States, 1998-2002.")

In 1996, the CDC began FoodNet, an active, population-based surveillance system that collects laboratory-confirmed cases of bacteria-caused food infections from 10 U.S. states. The organisms under surveillance now include Campylobacter, Cryptosporidium, Cyclospora, E.Coli 0157, Listeria, Salmonella, Shigella, Vibrio, and Yersinia. In 2001, an electronic reporting system made the effort even easier.

Last year, FoodNet surveillance areas identified 17,883 laboratory-confirmed cases of foodborne illnesses. The most common organism identified was Salmonella (6,790 cases), followed closely by Campylobacter (5,818 cases). In the United States, there are an estimated 76 million foodborne-caused illnesses each year, and 5,000 people die annually from foodborne illness. A majority of the time, the food was eaten at restaurants. And the most commonly reported contamination factor was "bare-handed contact by a food handler"; for outbreaks caused by bacteria, raw products contaminated by pathogens from animals or the environment was the most common causative factor.

For most of the foodborne outbreaks reported to the CDC, the cause isn't known. Of the outbreaks with a known cause, Norovirus and bacteria are typically to blame. It's important to realize that some pathogens that cause foodborne illnesses are still unknown, so laboratory tests to identify them don't exist.

In light of the recent crisis, a New York Times editorial called for a system to track foods from the farm to the table. But with a global food supply, tracking food from distant farms to U.S. plates would prove extremely difficult. (See "Increasing Food Quality Risks Are Affecting Global Food Supply Chain.")

The Department of Agriculture and the Food and Drug Administration (FDA) use a food-safety program known as HACCP (Hazard Analysis and Critical Control Point) that provides guidelines for all segments of the food industry to follow--farmers, harvesters, processors, manufacturers, and distributors among them. It was initially developed to keep space food safe for astronauts. In 1998, Agriculture implemented HACCP for meat and poultry processing plants; three years later, the FDA started implementing the concept. HACCP involves seven principles and uses a systems-analysis approach to food safety. Of course, properly implementing and administering such programs requires adequate funding, resources, and personnel--something that has been lacking in recent years. (See "Stronger Rules on Produce Likely After Outbreaks of E. Coli.")

The CDC provides extensive information for travelers going abroad to avoid foodborne illnesses, advising them to avoid all salads, uncooked vegetables, and unpasteurized milk and milk products. Paradoxically, many of these same foods are imported into the United States, yet the same precautions aren't provided. And they most certainly should be. For example, some locals in exporting countries only eat raw tomatoes after they've been peeled, and many disinfect their fruits and vegetables before eating them raw. (If you're interested, here are some instructions for peeling tomatoes and handling fruits and vegetables.)

Some people are taking food safety into their own hands and either seeking out locally grown produce and/or growing their own food.

The assumption that restaurant food is safe depends upon the ability of local health departments to conduct and enforce restaurant inspections. It also helps if restaurant workers are educated in safe food handling. (See "The Effects of Inspection Frequency and Food Handler Education on Restaurant Inspection Violations.") Ideally, health departments should make the results of their restaurant inspections publicly available. If not, the public should demand such information before eating out.

Just as importantly, food safety should always be a concern; even when cooking at home, people should always adhere to stringent hygienic practices. Irradiating food would destroy pathogens such as Salmonella in meat, poultry, and other foods, thereby helping reduce the risk of foodborne illnesses. The practice is endorsed by the World Health Organization and the American Medical Association, and nearly 40 countries allow it. But it's opposed by some consumer groups.

It's impossible to reduce the risk of foodborne illness to zero. While better surveillance and reporting has increased the identification and awareness of foodborne outbreaks, a complex, global food supply means that we should anticipate more foodborne outbreaks in the future. That said, individuals could do much more to reduce their risk of getting sick from food--especially if the source is unknown--by following the same common sense precautions that would apply if traveling in developing countries and by only eating at restaurants that passed their local health inspections.