Imagine if the CDC had access to all of your email, Facebook posts, credit card transactions, and location data from your phone and photos. It could do a reasonable job of finding the infection vectors for large populations (an unsanitary restaurant or school cafeteria, for example, or a friend who never washes their hands, or an infected spinach batch from country X, or a MRSA outbreak from hospital A, wing B). This information could be used to warn people to be extra careful in specific situations. Sadly, this is unlikely to happen in the near future.