Yeah, my biggest worry infection-wise is not some Cro-magnon superbug, because those would probably have wiped us out back then if they were that dangerous. It's the GM stuff being engineered in labs for "research" that some idiot will unleash through either negligence or malice. Read up on Ebola Reston if you want to know how close we've come already. Parvo virus in dogs is another example. It was being researched as a way to control the dingo populations in Australia when it escaped the lab and killed hundreds of thousands of dogs worldwide within a couple of years. Ebola in its native form is pretty nasty, but if it had a longer burn cycle(say 3-7 day incubation while contagious before symptoms manifest) it would be a civilization ender.
