// Pawns will have a 90% chance for at least one infection each year at 0% filtration, and a 0%
// chance at 40% filtration, scaling linearly.
// Let x = chance infected per roll
// Then chance not infected per roll = 1 - x
// And chance not infected on any roll in one day = (1 - x) ^ (60000 / 150) = (1 - x) ^ 400
// And chance not infected on any roll in one year = (1 - x) ^ (400 * 60) = (1 - x) ^ 24000
// So 0.10 = (1 - x) ^ 24000
// log (0.10) = 24000 log (1 - x)
// x = 0.00009593644334648975435114691213 = ~96 in 1 million
// Important Note:
// this function is called from Need_Sex::NeedInterval(), where it involves a needsex_tick and a std_tick to actually trigger this update_immunodeficiency.
// j(this is not exactly the same as the value in Need_Sex, that value is 0, but here j should be 1) std_ticks per this function called, k needsex_ticks per std_tick, 150 ticks per needsex_tick, and x is the chance per 150 ticks,
// The new equation should be .1 = (1-x)^(24000/kj)
p.health.hediffSet.GetFirstHediffOfDef(HediffDefOf.WoundInfection)==null&&// If the pawn already has a wound infection, we can't properly set the immunity for the new one