patient zero


Also found in: Medical.

patient zero

1. The first person to exhibit symptoms of an illness. The phrase originated during the AIDS crisis of the 1980s. My daughter was patient zero, the only one with a cold last week—now, she's very generously given it to the rest of the family.
2. By extension, the first case of or person demonstrating a particular issue or problem. This guy is patient zero for the crashing issue in the app, so let me see what he said in his original email.
See also: patient, zero
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