We don't know how the Ebola outbreak started. That's a problem.
(Vox) -snip- Though it took years for Snow's theory to achieve widespread acceptance, his approach is central to modern epidemiology. Investigating the source of outbreaks can prevent new cases, but it also gives us a better understanding of diseases and helps manage public fear. Even when infections have stopped, outbreak investigations are useful to develop strategies for preventing and, failing that, responding to future outbreaks.
Two recent outbreaks have demonstrated the necessity and the challenges of such investigations, almost two centuries after Snow's pioneering work. The first was the hantavirus outbreak that dominated headlines last month. Then, on May 17, the World Health Organization (WHO) declared a public health emergency of international concern, the highest level of global health alert, in response to an outbreak of the deadly hemorrhagic disease Ebola in the Democratic Republic of the Congo (DRC), which, as of June 2, had killed 62 people, with 363 confirmed cases. It's the 17th Ebola outbreak in the DRC and one of the largest on record. It has spread to neighboring Uganda, where, as of June 4, there are 16 confirmed cases, one confirmed death, and one probable case and likely death.
https://www.yahoo.com/news/science/articles/don-t-know-ebola-outbreak-111500069.html