Systematic risk assessment methods for the infection control professional.

Microbial and infectious disease risk models and tools are used to assess infectious hazards in the environment and to identify strategies to prevent or reduce these hazards. Although risk modeling of infectious threats represents a promising approach in applied epidemiology, there are inherent limitations to most models because of the multifactorial nature of the transmission of infections, the dynamic environment in which transmission takes place, and a paucity of available data to more fully specify model parameters. For example, the causal evidence for a link between hand hygiene and reduction in transmission of health care-associated infections is strong. Nevertheless, even though a simple mathematical model has been used to predict that very small increases in hand hygiene could bring endemic organisms under control, it is still impossible to assess precisely the extent to which an incremental change in hand hygiene will increase or decrease risk of disease transmission because of the complexity and ever changing transmission factors that arise within varying health care settings. Despite these limitations, predictive tools such as models or other systematic processes to assess transmission risk can be used to help structure decision