and valerie reyna, a professor of human development and psychology at cornell university. welcome to you both. dr. wells, when do we begin to think that this is a legitimate fear and when is it paranoia? >> that's an excellent question, but one that's difficult to answer in that i think anybody who has a concern has-- is justified to have that concern. and, therefore, we need to address that with good information. paranoia is probably too strong of a term. i would say that the concerns people have after all of the news cycles that we've been seeing in the last week or so, they're coming from my own family, my colleagues, my friends, and in all, at the end of the day, we can say today that this virus has not changed. the risk is still low for those of us that are not involved in health care, like these two heroic nurses that were really intimately involved with the care of mr. duncan, and, unfortunately, became infected. >> ifill: let me follow up with you on one more piece of that, which siwonder to what degree the language matters. when are theesizealate cases and when is