I was asked a really interesting question on a recent TV interview. I was asked about what lessons from HIV can be applied to Ebola. That I think about HIV a lot might seem strange given that it is now a completely treatable "chronic" infectious disease and not an explosive mysterious emerging infection.
But, HIV had its wild-child phase and it is the arguably the most successful emerging infectious disease ever.
HIV-1 spilled into humans from chimpanzees around the dawn of the 20th century, probably in Cameroon, and at first was likely a disease of bush-meat hunters and their close contacts who contracted the virus when butchering chimpanzees. Once industrialization connected these once remote areas to each other HIV-1 found a means to propagate amongst humans through sexual contact and the disease exploded.
The disease trickled on, accruing victims without notice. I always think if infectious disease physicians would have noted this trickle of patients before it became a worldwide epidemic decades later, it could have been contained (to some degree).
There's a story I've heard about a physician, Dr. Bila Kapita, recognizing the presence of the AIDS-defining illness Kaposi's Sarcoma in Kinshasa in 1975 and noting its presence in prior hospital records. I think this anecdote illustrates that if you look hard enough, you can find low-level "viral chatter" transpiring.
Ebola is similar in many respects. These explosive outbreaks represent stuttered forays into the human population and burn out because the virus is not efficiently transmitted between humans.
Studying these stuttered starts of emerging pathogens is what it means to be "tracking zebra".