Refactors virus spreading

code/datums/diseases/dna_spread.dm

@@ -2,7 +2,7 @@
 	name = "Space Retrovirus"
 	max_stages = 4
 	spread_text = "On contact"
-	spread_flags = CONTACT_GENERAL
+	spread_flags = VIRUS_SPREAD_BLOOD | VIRUS_SPREAD_CONTACT_SKIN | VIRUS_SPREAD_CONTACT_FLUIDS
 	cure_text = "Mutadone"
 	cures = list("mutadone")
 	disease_flags = CAN_CARRY|CAN_RESIST|CURABLE
@@ -11,7 +11,7 @@
 	var/datum/dna/original_dna = null
 	var/transformed = 0
 	desc = "This disease transplants the genetic code of the initial vector into new hosts."
-	severity = MEDIUM
+	severity = VIRUS_SEVERITY_MEDIUM
 
 
 /datum/disease/dnaspread/stage_act()