There is not much known about the Chimeran Virus other than that it is spread through conversion centers. Where the Chimeran Virus came from is unknown but there are many theories varying from Russian Bio experiments.
Many people believe that at the start of World War I the Russians discovered something mysterious about the Chimeran DNA. Something they noticed that got their attention. They harnessed it and made a new kind of creature, The Cloven. Everything was just fine for a while. But then the Cloven started "evolving" and turned into Chimera. The Chimera started turning into more and more advanced types. Their conversion centers and towers arouse from the ground. Mysteriously no one knows how. But then the Chimera started evolving to more and more advanced types. Eventually evolving fully into Carriers. The Carriers brought human beings back to the conversion centers and soon the world was flooded with Chimera.
Carriers came and abducted people more and more. Tons and tons of human were mass produced coming in as regular human and coming out as Chimera. People worked constantly together on a cure. Mainly Dr. Rayne Bouchard and her father were two of the main scientists working on the cure.