I enjoyed this story. The thought that strikes me is whether he has been the carrier all along and has been the force that has caused the expansion of the virus.

The one suggestion I would give, if you were going to rewrite this for any purpose, would be to change some of the wording so that it doesn't sound so much like it's happening right now. As an example, I feel as though "mowing the grass" might be a word choice that isn't implicit to the setting.