Very interesting, thanks for taking the time to give a detailed reply.
with very sophisticated bioscience, such a person killer that had overlapping qualities could be created.
How sophisticated are we talking? Is this something conceivable for sufficiently motivated modern day humans with access to up to date knowledge, or theoretically possible but extremely difficult?
The latter. I've read of limited successes in other fields of research (no one is publicly trying to make something like this) that indicate it's just barely possible, maybe, with some luck.
One nasty thing is that the virus doesn't have to be safe. It just has to work, and it's not a problem if it permanently damages the people it doesn't kill. So, creating a weapon like this is fundamentally much easier than trying to create, say, a treatment for cancer using similar methods.
The FHI's mini advent calendar: counting down through the big five existential risks. The fourth one is an ancient risk, still with us today: pandemics and plagues.
Pandemics
Current understanding: high
Most worrying aspect: the past evidence points to a risky future
The deathrates from infectious diseases follow a power law with a very low exponent. In layman’s terms: there is a reasonable possibility for a plague with an absolutely huge casualty rate. We’ve had close calls in the past: the black death killed around half the population of Europe, while Spanish Influenza infected 27% of all humans and killed one in ten of those, mostly healthy young adults. All the characteristics of an ultimately deadly infection already exist in the wild: anything that combined the deadliness and incubation period of AIDS with the transmissibility of the common cold.
Moreover, we know that we are going to be seeing new diseases and new infections in the future: the only question is how deadly they will be. With modern global travel and transport, these diseases will spread far and wide. Against this, we have better communication and better trans-national institutions and cooperation – but these institutions could easily be overwhelmed, and countries aren’t nearly as well prepared as they need to be.