patient zero

Etymology
Originally patient O (standing for out of California), referring to, a superspreader of AIDS who was at the time erroneously believed to have introduced the virus to the United States. The letter O was later misinterpreted as a zero.

Noun

 * 1)  The initial patient in the population of an epidemiological investigation.
 * 2)  The source or origin of something.
 * 1)  The source or origin of something.
 * 1)  The source or origin of something.
 * 1)  The source or origin of something.
 * 1)  The source or origin of something.