Natural Selection - The process by which certain heritable traits that contribute to the survival and reproductive success of an organism become more widespread within a population over successive generations.⏎
National Institute of Allergy and Infectious Diseases (NIAID) - Part of the U.S. Department of Health and Human Services and the National Institutes of Health, NIAID conducts and supports basic and applied research to better understand, treat, and ultimately prevent infectious, immunologic, and allergic diseases.⏎
Prion - A causative agent of infectious disease that is composed primarily of protein.⏎
Outbreak - An unexpected increase in the incidence of a particular disease over a given time period and geographic range. A general term that may refer either to an epidemic or a pandemic.⏎
Nanometer - A unit of length equal to one one-billionth (1 x 10-9) of a meter.⏎