I've been terribly selfish and was focused more on my own health. The hospital could give you a better idea.

[Tony has been using his own nanites to combat the foreign invaders and which does take up a considerable amount of his attention.]

I can transfer my own nanite fleet through direct contact with my body fluids if you needed somewhere to start. This is likely programmed to work independently, but they might use the same idea. I don't think there's enough people affected for it to be through the water or food supply.