Addressing Susceptibility in Microbial Pathogen Risk Assessment

As concern for vulnerable subpopulations has grown, susceptibility has become a more important element in risk assessment and management processes. However, there is little consensus on how to incorporate or model the concept effectively in microbial pathogen risk assessment (MRA). Susceptibility is fundamentally a complex concept. There are many different definitions for it, reflecting the principles and viewpoints of the fields that contribute to risk assessment. Although susceptibility needs to be addressed in every step of the risk management paradigm, it has not yet been fully integrated into risk assessment, one step within the paradigm. Many factors are involved in characterizing and modeling susceptibility, but little is known about the relationships of many of the factors and many cannot be reliably measured. Recent MRA frameworks and case studies were reviewed for their approaches to susceptibility. Themes identified included limited or no explicit conceptualization of susceptibility in the problem formulation, limited data to assess susceptibility, heavy or exclusive emphasis on susceptibility in the health effects portion of the model, primary focus on host characteristics, and little consideration of susceptibility in risk characterization. Recommendations to improve approaches to susceptibility in MRA are presented.