It's a joke about the plot of The Last of Us, which pins the zombie outbreak on a fictional cordyceps variant that zombifies people (inspired by ones infecting ants or spiders).
I know, I was also joking, and I mistakenly assumed that would be obvious because who would write, "oh no I just ate some cordyceps!!" but then I looked it up, and I guess you can in fact eat those, and people do, so the joke is on me.
