FAQ: Emerging Microbiological Food Safety Issues

Why focus on emerging microbiological food safety issues?

Recent scientific advances have created the opportunity for new insight into microbiological food safety issues. Our current policies and controls have served us well, but improvements are needed. With new information and tools, we can now create food safety management systems that use science to assess risk and focus our efforts in a flexible and effective manner. Knowing that change is inevitable, we can look ahead to spot new issues as they arise and be prepared to respond.

In choosing to focus on emerging microbiological food safety issues, IFT hoped to emphasize the complex, everchanging nature of microbiological food safety. Pathogens evolve, people’s behaviors and susceptibilities differ and change, and production and processing developments modify the microbial environment. We cannot expect to “solve” the problem of microbiological food safety to the point of having a zero-risk food supply. On the other hand, we have the opportunity to look forward and address issues before they become pervasive.

Why doesn’t the report address bioterrorism?

Work on this Expert Report began long before domestic terrorism was at the forefront of America’s consciousness. IFT considered changing the report’s focus and decided to continue producing the original report, because microbiological food safety remains an important issue that needs to be specifically addressed.

Many aspects of this Expert Report also have significance for bioterrorism issues. The description of the various pathogens and illnesses they cause could aid in diagnosis of an outbreak of foodborne illness, whether accidental or intentional. Understanding pathogen characteristics and their interaction with the environment will help identify points in the food chain where pathogens could be intentionally introduced. Integrated surveillance for foodborne illness could help spot any intentional contamination quickly, and our understanding of the food system would enable officials to rapidly minimize the danger. Improvements in consumer food safety practices could dramatically reduce the effectiveness of introducing pathogens into the food supply.

Why do new food safety issues emerge?

 New food safety issues emerge for many reasons. Sometimes, a microorganism evolves to become pathogenic, or a pathogen evolves to become more virulent. Other times, the change is linked to the people at risk for foodborne illness. For example, they may become more susceptible to illness if their immune system is not functioning at an optimal level, or they may change which foods they eat, potentially exposing themselves to different pathogens. Changes to the microbial environment can provide new vehicles for pathogen contamination of foods. The interrelationship of these factors is so complex that it is impossible to describe all the reasons a food safety issue could emerge.

In addition, a food safety issue can appear to emerge because we have new methods to identify it. The issue may have been around for years, but until we identify the pathogen and link it to food, it doesn’t factor into our understanding of food safety.

How many foodborne illnesses are there each year?

The Centers for Disease Control and Prevention (CDC) estimates there are 76 million cases of foodborne illness each year, resulting in 325,000 hospitalizations and 5,000 deaths.

How many foodborne pathogens are there? We don’t know. More than 200 known diseases are caused by pathogens, their toxins, or other substances transmitted through food. A cause has not been identified for more than half of all recognized foodborne disease outbreaks, indicating that the real number of disease-causing agents is likely to be much larger than 200. The recognized microbiological causes of foodborne illness include viruses, bacteria, parasites, and toxins produced by algae and fungi.

What are the worst pathogens?

 That depends on how you define “worst.” According to CDC estimates, Norwalk-like viruses cause approximately 9.2 million cases of illness each year. However, of the estimated 9.2 million cases, only 124 people die, a fatality rate of 0.001%. On the other hand, Vibrio vulnificus causes a mere 47 cases each year, but nearly 40% are fatal. When developing food safety management polices, we struggle to balance the incidence of illness against the severity of illness, because both are important.

What are the most dangerous foods?

Again, that depends on how you look at the issue. Certain foods are especially dangerous for some people because of the likelihood that they contain a particular pathogen. For example, Listeria monocytogenes rarely causes illness in the general population, but if a pregnant woman becomes infected, the developing fetus also may become infected and may die. Foods that are safe for most people may be deadly for a small group of people. Some foods may be rarely contaminated, but the pathogen of concern may be especially virulent. For example, the incidence of Escherichia coli O157:H7 in raw ground beef is approximately 1%, so the risk the food will be contaminated is relatively low. However, only a few cells of E. coli O157:H7 are necessary to cause illness, so when a contaminated food is consumed without sufficient cooking, illness is more likely. In general, raw foods often present a higher risk of foodborne illness than properly cooked foods, because many pathogens are sensitive to heat.

Do people really die from foodborne illness?

Yes, they do. Although people correctly associate foodborne illness with flu-like gastrointestinal symptoms such as vomiting and diarrhea, these are only some of the symptoms caused by foodborne pathogens. Some pathogens invade deeper tissues or produce toxins that are absorbed and cause systemic symptoms, including fever, headache, kidney failure, anemia, and death. Other pathogens are linked to chronic illnesses, including certain kinds of cancer.

Do cooking and refrigeration eliminate the risk of foodborne illness?

No, but they are an important part of proper food handling and preparation practices. All pathogens may not be destroyed during cooking, and properly cooked foods can be recontaminated if they are not handled properly. Foods that will be consumed raw, such a produce, may be contaminated during production and distribution or through cross contamination during preparation. Although refrigeration limits the growth of many pathogens, some pathogens can multiply at refrigeration temperatures. Others do not increase in food but they survive until they reach the human host. If foods are stored under conditions that are too warm, pathogen growth may be enhanced. For food safety, refrigerators should be maintained at 40 F or cooler.

If food looks and smells ok, how can it still make me sick? The microorganisms that cause a food to appear spoiled are different from the foodborne pathogens that make people sick. Spoilage microorganisms are rarely pathogenic. In fact, spoiled food may be less likely to have dangerous levels of pathogens, because the spoilage microorganisms will have been competing with the pathogens for environmental factors such as nutrients and space. Unlike spoilage microorganisms that often produce changes in a food’s odor and color, pathogens usually do not produce observable changes in food.

What part of the food chain poses the greatest risk for foodborne illness?

 It is difficult to determine. Each part of the food chain poses different risks. For example, the relatively uncontrolled environment of production agriculture may present numerous avenues for food to become contaminated by pathogens. The processing environment can expose pathogens to environmental stresses that make the surviving microorganisms better able to not only survive future processing controls but also to overcome the body’s defenses and cause illness. Each pathogen/ food combination represents a combination of many factors. Some may be best addressed through good agricultural practices to prevent contamination in the first place. Others may be best addressed by a control step in the processing environment to inactive any pathogens on the food. Others may be best addressed by consumer food handling and preparation practices. Microbiological food safety is truly a farm-to-table issue.


Recognizing that food safety is a fundamental and continuing issue, the Institute of Food Technologists commissioned an expert panel to review the available scientific literature related to emerging microbiological food safety issues. The panel’s report is divided into seven sections: Introduction, Pathogenicity, Human Hosts, Microbial Ecology, Application of Science to Food Safety Management, Next Steps, and Conclusions. Copies of the report are available at www.ift.org. Founded in 1939, IFT is a 28,000 member nonprofit scientific society for food science and technology.