patient zero

[ pey-shuhnt zeer-oh ]

noun

1. Pathology. the first known carrier of infection in an outbreak: index patient.

   Public health officials are tracing all contacts of infected patients, trying to work their way back to find patient zero.

2. the person or thing that is believed to be the point of origin for any spreading effect, status, or event, especially if negative:

   One rowdy new student was patient zero for all kinds of classroom chaos and problem behaviors.

Word History and Origins

Origin of patient zero¹

First recorded in 1985–90