system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is patient zero of such significance?

The wife and I yesterday watched "contagion" and we were wondering, why there is always such a hubbub about "patient zero". What's so special about the first person to catch a transmittable disease, that the second or third or four-hundredth person does not have?
gpt
Viruses mutate as they travel to different hosts, so the first patient to get it has the most basic form of it that has the most in common with the daughter strains, which may evolve in completely different directions.  Thus, if you find a cure based on the original patient, is has the highest likelihood of working on the daughter cases.