...linger in society, the more mutations you allow. Transmissability is one threat, but it could also become more lethal, have more terrible long term side effects etc. Spanish Flu did this and its just rolling dice every day we leave it roaming out there. From an evolutionary standpoint, the virus does best when it infects the maximum number of people for the longest window without killing them, so they can go on and infect more. But like Ebola, it can get deadlier too even though that kills the hosts and limits the spread. We have been playing a very deadly gambling game, Crazy!!!