The scientists were trying to create a substance that could increase a persons muscle size, tone and strength. They had attempted many tests on human captives however all had failed by over enhancing the subjects muscles and causing immediate exhaustion, in some cases the subjects had become gay as a side effect.
The scientists continued testing and created a virus that would transform its subjects if inhaled, ingested or transmitted through contact. It wasn't long after until the government discovered their methods and apprehended them, attempting to destroy the project, phials of the muscle enhancer were smashed causing it to leak into the air and water, now anyone who inhales or ingests the virus will permanently be affected by it.
Who becomes infected first: