There are very, very few outbreaks where we don't eventually figure out the source. Like, can you spin the theory that we're missing them? Sure. But there's a

There are very, very few outbreaks where we don't eventually figure out the source. Like, can you spin the theory that we're missing them? Sure. But there's a pretty strong absence of evidence there, despite a field that's actively looking constantly (and where showing that would further the political and scientific careers of a number of people).