Environmental Control of Transmissible Emerging Infections

Diverse paths have been documented for infection transmission between individuals through the environment. The roles played by these paths in the transmission system of any agent and the effects of environmentally based actions to interrupt those paths are largely unknown. Methods to make such determinations for emerging or bioterrorist infections are lacking. To overcome this deficiency, the Center for Advancing Microbial Risk Assessment (CAMRA) is developing models and conducting experimental and observational studies. Analysis of CAMRA models that incorporate multiple transmission paths demonstrates that which path is important is not only a function of how an agent is excreted, how well it survives under different conditions, and what behaviors lead to exposure. The nature of human movement at a venue where transmission occurs and how accumulation of exposure doses occurs over time are also strong determinants of which transmission path is most important to control. For example, in influenza the relative importance of hand-fomite routes versus aerosol paths is likely to be determined by these factors. Unfortunately data is currently insufficient to resolve which paths will dominate. CAMRA models are being used to help design new study methods that will provide the data needed to resolve this issue. One context for which these methods are being designed are the CDC sponsored studies of the relative importance of mask wearing, hand decontamination, and surface decontamination in controlling influenza transmission.