Boffin has suggested that some of the techniques being developed to combat illnesses like cancer could be used to create targeted bio weapons.
www.theguardian.com/science/2017/jul/31/bioweapons-cancer-moonshot-gene-editing
It's clear this could happen, I mean a few years ago students were able to create a synthetic virus using genetic material they could order in the post and there has been a trend in the US for bio hacking clubs (growing luminous algae using genes from jellyfish and what not).
Making a virus through is very different from a virus evolving, and controlling all the many attributes the virus needs to thrive is very difficult. A man made virus is likely to be unstable and thus may not be effective.
Still gives you pause for thought.