Greek Mythology: miasma
miasma is a pollution that is perceived as a death of sorts. If a family member is murdered, the family should avenge that member’s death by killing the killer. If the family doesn’t, then the spirit of the murdered member would reanimate and haunt the family or the murderer. A family who doesn’t avenge their dead family member is said to have miasma. Miasma is treated like a disease.
You don’t want to associate yourself with anyone who has it because it might rub off. Those with miasma had to be purified in order to rejoin society. In the purification ceremony, the people were washed, and then wrapped in swaddling clothes and hade to make a show of feeding them at the breast by drinking milk. Apollo is in charge of this ritual = Apollo Catharsius.