Humans as Hosts of Foodborne Disease

A number of factors that relate to the human host have a major impact on the occurrence and severity of foodborne disease. The host’s age, gender, place of residence, ethnicity, underlying health status, and knowledge, attitudes, and practices related to health and diet all have important bearing on foodborne illness. The health of the host affects the individual’s susceptibility to infection and illness, and the host’s dietary and hygiene practices affect exposure to pathogens. From medical and behavioral perspectives, human host factors can be altered by modification of susceptibility or elimination of exposure.

Clinical Disease

Most infectious foodborne illness is characterized by acute symptoms that are limited to the gastrointestinal tract, including vomiting and diarrhea. These illnesses are generally limited in both duration and severity, and most patients without underlying illnesses or malnutrition recover without medical treatment or require only modest supportive care. These illnesses can be especially difficult to quantify because medical treatment is not sought. However, some pathogens cause gastrointestinal symptoms that are more severe and take longer to subside, especially in sensitive populations such as young children, the elderly or people with AIDS.

Not all foodborne disease is limited to the gastrointestinal tract. Some foodborne pathogens invade deeper tissues or produce toxins that are absorbed and cause systemic symptoms, including fever, headache, kidney failure, anemia, and death. In addition to acute illness, some foodborne pathogens cause chronic illness, often within sensitive subgroups of the population.

Resistance and Susceptibility

Humans are protected from infectious foodborne disease by a variety of immune system mechanisms. When all of these systems are functioning optimally, the chance of foodborne illness is reduced. Many factors cause these systems to function below optimal levels, increasing the likelihood of illness. In addition, some foodborne pathogens have found ways to evade or trick the body’s defensive mechanisms.

Susceptibility to infectious disease is the inability of the host’s body to prevent or overcome invasion by pathogenic microorganisms. Susceptibility to infectious disease is increased by conditions that alter the host defenses and suppress the function of the immune system. Many factors cause changes in the immune system function, such as age, health conditions (e.g., AIDS, cancer), pregnancy, nutritional status, and antacid/medication use. Factors that suppress the immune system increase the risk of foodborne illness.

An important contributor to microbial pathogenicity and human illness is the changing human population and its behavior. The portion of the U.S. population that is elderly continues to grow, and large numbers of individuals have conditions necessitating the use of immunosuppressive drugs or drug combinations with unknown effects, potentially increasing their susceptibility to foodborne illnesses.

Modification of Risk

Because of the significance of the human host in foodborne illness, it is appropriate to consider host-related opportunities for control or mitigation of susceptibility to illness. Although complete protection is currently out of reach for many pathogens, approaches such as immunization and probiotics can decrease human susceptibility to certain foodborne illnesses. Coupling these approaches with efforts to mitigate exposure would further boost our ability to control foodborne illness of infectious origin.

While many host factors that influence infection, occurrence and severity of illness are associated with human physiology, the factors that influence exposure to foodborne pathogens are often tied to human behavior, specifically consumption, food handling, and preparation behaviors. Which foods are consumed and how those foods are prepared affect an individual’s risk of foodborne disease.

Despite education efforts, consumer behavior continues to play a significant role in exposure to foodborne pathogens. Consumers are sometimes unaware of or inattentive to their personal ability to reduce the risk of foodborne illness. Hygiene, food preparation, and food handling and storage practices all contribute to pathogen exposure.

The combination of proper hygiene and sanitation related to food handling and preparation, appropriate methods of refrigeration and freezing, and thorough cooking of foods comprises a very effective approach to preventing foodborne illness. Because food manufacturers cannot consistently provide foods guaranteed to be free of pathogens, the individuals preparing the food must use proper knowledge, attitudes, skills and practices to achieve food safety.


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.