So i recently saw a post claiming that people would get automatically infected in the mushrooms biome, so i made an all mushroom biome world with infertile inmortal people to see if they're ever got infected, i also turned on the option to see mush infection in the debug menu to see if any animal gets it, but after more than 400 years nothing happened, so i think it's safe to assume that the mushrooms biome it's safe 👍🏻