Sam: “Presumably there is also a physical danger involved in Tzara’as.”
That’s a presumption, I’m awaiting a source or proof. Admittedly my proof to the contrary may not be iron-clad,but I have yet to see any indication supporting your position. the encyclopedic work Shmiras HaGuf v’HaNefesh discusses atlengtht various opinions regarding the severity and source of the prohibition of incurring danger. He makes no distinction between physical and spiritual danger. Of course his omission is not a conclusive proof either.
I think that at Shishim it is considered to not be physically present, as the Rambam refers to it as ????? ????? ??????. This opinion would seem to be mutually exclusive to applying Sakanta Chamura mi’Issura to 60x.