I don't know why you emphasize rogue and non-state actors. It seems equally likely to me that it would be done by America. America is the only country who deployed nukes (Japan) and chemical weapons (Vietnam) on massive scales.
I can agree that access to bioengineering tooling is easier and cheaper than ever, and thus eventually it stands to reason that a nobody in his basement could engineer a lethal novel virus and lose control of it.
I can agree that access to bioengineering tooling is easier and cheaper than ever, and thus eventually it stands to reason that a nobody in his basement could engineer a lethal novel virus and lose control of it.