Disease Refactor (#2021)

code/datums/diseases/_MobProcs.dm

@@ -1,6 +1,7 @@
 
 /mob/proc/HasDisease(datum/disease/D)
-	for(var/datum/disease/DD in viruses)
+	for(var/thing in viruses)
+		var/datum/disease/DD = thing
 		if(D.IsSame(DD))
 			return 1
 	return 0
@@ -39,7 +40,7 @@
 		var/datum/disease/DD = new D.type(1, D, 0)
 		viruses += DD
 		DD.affected_mob = src
-		DD.holder = src
+		SSdisease.active_diseases += DD //Add it to the active diseases list, now that it's actually in a mob and being processed.
 
 		//Copy properties over. This is so edited diseases persist.
 		var/list/skipped = list("affected_mob","holder","carrier","stage","type","parent_type","vars","transformed")
@@ -147,6 +148,9 @@
 
 
 /mob/living/carbon/human/CanContractDisease(datum/disease/D)
-	if(dna && (VIRUSIMMUNE in dna.species.species_traits))
+	if(dna && (VIRUSIMMUNE in dna.species.species_traits) && !D.bypasses_immunity)
 		return 0
+	for(var/thing in D.required_organs)
+		if(!((locate(thing) in bodyparts) || (locate(thing) in internal_organs)))
+			return 0
 	return ..()