Codename: Outbreak

During a routine observation of the night sky, astronomers registered a new object in the Ursa Major constellation, a mid-size comet. The strange object was moving at a tremendous speed and could soon be seen with the naked eye in the night sky. State authorities began preparing for the possible ensuing catastrophe and evacuated all major cities.
Humans got ready for the worst though the worst was yet to come. Your mission begins on a nearly decimated planet Earth ravaged by meteors... and worse, sinister alien spores! These spores leach onto living beings and mutate them into hideous killing machines. Command your two-man task force to eradicate this terrible infestation and salvage what is left of the planet before it's too late.