The Neurax Worm is a parasite that stays on the brain of its host, it was a frozen parasite that was found and now will try ot infect all humanity, it will try to use you to infect others making you go arround and make it eggs get on places that people could get infected doing whatever is needed to achieve that, but if you dont do what the parasite tells you, you will have serious issues, the parasite will slowly evolve controlling you more and more over time.