"Patient Zero" is the common name for an individual supposed to have been the starting point of a viral outbreak or pandemic.
But, did you know that the original "patient zero," Gaetan Dugas of the HIV epidemic, was originally labelled "Patient O," that's the letter O as in outside of California?
And it turns out that Dugas was not responsible for bringing AIDS to New York, as some shrill fear-mongers said in the press. The virus was already present there when he was spreading it. But then, it's easier to point fingers at a boogeyman rather than understanding science or just accepting the vagaries of biology.