I feel like I was missing some extra clue, but I did quite a lot of searching and could not find the infected person I was tasked to find. That being said I love all the character designs and I am impressed by the extent of this game.
if you go to the hospital it will show the "sick" person on your mini map. The small screen does make it hard to spot the person just walking around.
Got it! I'll have to take another go at the game.