The word of the day is zoonosis:

zooˈnosis n. /-ˈnəʊsiːz/ (also zooˈnoses)  [Greek νόσος disease] a disease communicated from one kind of animal to another or to a human being; usu. restricted to diseases transmitted naturally to man from animals. (OED)

"But after September 11, 2001, he became preoccupied with viruses and terrorism.  He had been planning to fly to New Jersey that day, and the drive home from the airport took three hours.  Along the way, he thought about the potential use of viruses: 'I just thought, you know, flying a plane into a building - for a sort of low cost, you create a very high-cost event.  If I were a terrorist, I would do a virus.  This came to me as I was driving home, thinking, Things are a lot scarier if you could take a dog with some zoonotic virus and let him go in some neighborhood and the next thing you know people are tying up the whole medical system.'"

 - David E. Hoffman, "Going Viral: The Pentagon takes on a new enemy: swine flu", 31 January 2011 The New Yorker