This question may possibly be a fit for English Language or History stackexchange.
Recently it was widely reported in the media about the results of new genetic testing of early HIV samples. The reports showed two major flaws against the usefulness of identifying a Patient Zero in that outbreak:
the man described in the 1980s as Patient Zero in the AIDS outbreak was in fact not the source of the outbreak, but a typical case several genetic steps removed from a putative first case in the US. As a result the notion is "both ethically and scientifically challenged".
The notation used in the actual samples in that original case were marked "Patient O" with an Oh, not "Patient 0 (Zero)". 'O' for "outside California. It was a typo or an accidental misreading to call the case Patient Zero.
Looking at wikipedia we can see that most uses of the term seem to refer to the AIDS case. I've also seen the term used in zombie movies, but this may not be a reliable source for medical terminology. Is or was the concept of a patient zero ever used in medicine or epidemiology or virology, or was the concept created out of whole cloth via a mistaken translation by non-medical observers?