[CBC] We still don't know where the 2019 novel coronavirus came from. The leading suspicion is an animal host ‐ a bat, likely ‐ infected another animal that has more contact with humans. That's how the 2012 MERS (Middle East Respiratory Syndrome) outbreak is believed to have played out. A bat, at some point in the past, infected a camel, which may have sneezed on a human.
One of the reasons the human and animal worlds are bumping up against each other is a changing climate. Research suggests that warmer winters and springs are keeping bats, for example, around longer because the insects they feed on also like the warmth. And this may affect the spread of diseases bats carry.
"Climate change, coupled with other human environmental changes like urbanization and habitat destruction, is bringing us closer to wildlife," said Dr. Katie Clow, a professor at the Ontario Veterinary College at the University of Guelph. "So there's this very complex interplay of many different changes happening all at the same time."