Via Newsweek, a long but very informative article which takes deeper look at diseases which sources are from animals:
" Animal-based diseases account for 75 percent of newly emerging infectious diseases, including H1N1. Can health agencies work together to stop their spread?
One year ago this month, Dr. Anne Schuchat took the mike at one of the government's first press conferences about a worrisome new flu outbreak. Schuchat, director of the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases, was trying to clarify what public-health officials knew about a virus that had sickened patients in Mexico and the United States. No, this was not bird flu, Schuchat told reporters listening in by phone from around the country that April day in 2009. That virus, technically known as H5N1, had been circulating since 1997, mainly in Asia. This was swine influenza, or, as it would soon be called, H1N1. "We're talking about a new virus," Schuchat said, referring to the novel form of H1N1, "a combination of a couple of different components of swine, human, and bird influenza."