Thousands of years ago, there was a man who was infatuated with a woman in his tribe. His father was a chief and arranged for them to be married, but things were rough. The girl was manipulative and took advantage of the obsession of the boy to gain the food he hunted and a room in his hut. He came back from hunting one day and did not see her in his hut, so he went to ask his father. To his horror, he found his wife sleeping with his father, and dragged her out by her hair to be shunned by the tribe. However, all of the men simply laughed because they had all already slept with the woman. The man became furious and went into the forest to make a deal with an evil god of bacteria. He slaughtered a monkey, an ibex, and a cow then fed to the spirit their bones, flesh, and dung. In exchange, the evil god would cause the girl a contagious rash that caused red bumps and pain to her and all who would engage in sex with her. He fled the town and made sure never to return so he would not catch the curse.
However, over thousands of years the curse put on humanity continued to spread until it became common. Modern medicine has not created a cure but ways to manage it. Many people died of the curse in primitive times, but the virus has evolved over so much time that it is now perfectly adapted to hide in the body and spread without causing the death of its host. Some magicians have said they are able to cure herpes and HIV through supernatural methods, but this may be somewhat difficult to do consistently or replicate on a larger scale and likely requires involvement of powerful love deities such as Venus or Aphrodite.
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