actually. Dr.cain found X roughly 30 years after Dr.Light and Dr.Wily died. After Dr.Cain found X, he built sigma and a bunch of other robots called Reploids. They were all created "like X" to have emotions and can make choices on their own. However X thought more deeply, almost identical to a human can. While Dr.Light created X. Dr.Wily was creating his own "Reploid" Around the same time, this was Zero. Dr wily tried cramming as much Bassinum into Zero as he could, to make him very powerful. Too much so that he was "purely evil" and was actually the first Maverick. Zero was released Before X was, not by Dr.cain however. Later Zero had a battle with sigma, where he was at an advantage. He was about to destroy Sigma when his blue gem started glowing with a W on it (dr Wily's symbol) and he started malfunctioning. Sigma took this change to bunch his blue gem thingy, breaking it in the process, but also ridding Zero of his "Maverick" mind and infecting Sigma with the maverick virus instead. (watch: www.youtube.com/watch?v=nPlTvJ… ) Sigma, then later actually got fully infected with the maverick virus in the "day of sigma" OVA in Maverick hunter X. So The maverick virus was actually started by Dr.Wily, First put in zero which spread to Sigma, who made the virus spread like wildfire. So if anything. Zero is the one responsible it.