The virus doesn’t change itself. The strains that are better able to incubate longer and spread easier, and result in a lower fatality rate fare better, having a non-human reservoir helps as well, so that even when the germ appears gone, it can re-emerge much later and cause another outbreak. Given that we also have pigs and bats in America, we should be extra sure that potential infectees do not have contact with possible non-human reservoirs .
viruses like Ebola are notoriously sloppy in replicating, meaning the virus entering one person may be genetically different from the virus entering the next. The current Ebola virus’s hyper-evolution is unprecedented; there has been more human-to-human transmission in the past four months than most likely occurred in the last 500 to 1,000 years. Each new infection represents trillions of throws of the genetic dice.
