It is possible, given recent publications, that synthetic smallpox could be manufactured by terrorists and released, destroying the West, and maybe themselves for their troubles:
http://www.shtfplan.com/headline-news/scientists-freak-out-over-pandemic-potential-of-genetically-engineered-smallpox_10152018
https://futurism.com/smallpox-synthesis-pandemic
“Earlier this year, scientists published a paper describing how they pieced together segments of DNA in order to bring back a previously eradicated virus called horsepox. The paper, written by two University of Alberta researchers and the co-founder of a New York pharmaceutical company, was controversial because, as various experts told the magazine Science, someone could use a very similar process to bring back a related virus: smallpox. Smallpox, you’ll recall, killed hundreds of millions of people before the World Health Organization declared it eradicated in 1980. That was the result of a long vaccination campaign — so the idea of piecing the virus back together from bits of DNA raises the specter of a horrifying pandemic.