According to research by an international team of researchers Smallpox might have merged way later then we previously thought. Tissue samples were taken from a Lithuanian child mummy that us dated back to the 1600's. It was concluded that the cause of death was smallpox, but not exactly the strain we cause just a hundred years ago. Reconstructing the full RNA sequence of the smallpox virus strain and compared the results to more recent samples. With this information the team was able to make a time line of the smallpox virus and piece together information about the different strands. While looking at the timeline for the diseases the rate of mutations was also studied and their was found to be two major strand groups, and all related back to a simple common ancestor. With the information uncovered about the common ancestor it was evaluated that smallpox must have not always been such an epidemic. If small pox had been an epidemic for the thousands of years that it has been around researchers would not have been able to find a common ancestor since it would have diverged tremendously over time.
This article is extremely fascinating because with a small sample from a mummy that is thousands of years old they were able to make a time line for small pox and better understand how the virus grew and mutated. With more data like this hopefully we can come to better understand how viruses are spreading so rapidly and diverging out of nowhere. With this knowledge we can better understand and develop more vaccines and save thousands of lives.
For more information on the history of smallpox go to - https://www.cdc.gov/smallpox/history/history.html
Main article: http://blogs.discovermagazine.com/d-brief/2016/12/08/child-mummy-smallpox-timeline/#.WQfiYIn5601