I haven't really thought on the theory of it very much yet but I think it would be a brilliant piece of research to flesh out (I hope they are able to carry on with it).?
It just got me thinking about how you would effectively track patients movement through a hospital. Ideally the movement would have to be monitored anonymously so people didn't feel they were being tracked. I wonder if one technique would be to give all people coming into the hospital an RFID tag (perhaps a card) that they can carry around with them. At each entrance to a room / ward / area the RFID scanners (similar to those used at the entrance to shops but hopefully less intrusive) would pick up the tags and the individual ids and track them.?
With the ids and the rooms they went to you can build up a list of edges to the nodes and see which areas are hubs for movement. Using that you could map it against the data of infection outbreaks and try and look for patterns.?
Obviously this is a very simplistic view of the problem. For a start the cost could be astronomical. Would people need to give the tags back? How could you control that? There are plenty of questions but it's worth thinking about.?