A microscopic protein particle similar to a virus but lacking nucleic acid, thought to be the infectious agent responsible for scrapie and certain other degenerative diseases of the nervous system.

• 朊病毒（感染性蛋白质）极微小的蛋白质微粒，类似于病毒，但不含核酸，被认为是绵羊痒病和其他的一些神经系统变性疾病的传染介质