From what I understand, Fort Smith Labs was creating a cure/serum for a specific or multiple diseases. The cure/serum required a living creature in order to test the effectiveness. This was in the form of a deer for Gus (duh). A living female was needed in order to harbor the embryo which was the actual subject of the testing. The plasticity of the genetics and stems cells make a living embryo prime for testing the changes taking places after an injection (I don't know if this is true but it sounds reasonable enough). After one (or multiple) injection(s) at some point(s) during the pregnancy, the mother's embryo delivered the desired genetic changes sought after by the Fort Smith researchers. They had several (possibly hundreds) of other test subject animals. They allowed the embryo to develop further in order to use the being as a biological 'piggy bank' (in the same way that the hybrids are now being harvested in an attempt to cure 'The Sick'--which also leads me to lean towards the mother/test subject being animal and not a human). After a certain amount of time throughout the pregnancy, it was determined that the fetus was forming into a human (rather than a deer partly infused with human genetics and the sought after cure). The researchers continued with the pregnancy and the birth of the child (Gus) who they could no longer ethically harvest due to the embryo's emerging human-like nature. At this point, they had already injected multiple other mothers/embryos because they were testing on multiple species at once in case the serum/cure was only compatible with a certain genetic code. The cure/serum that they made happened to be compatible with all species and they were ethically obligated to bring all the hybrids to term. 'The Sick' was an unforeseen natural virus that developed in one or more of the hybrids and it was propagated via airborne spread when the affected hybrid(s) was born. Thoughts?