Some regard COVID-19 as a warning to prepare for the eventuality of a far more lethal plague. I wondered whether dramatization of this threat would serve a good purpose. I think it will, provided the drama is tempered with science.
(YouTube) The Satan Bug is a 1965 movie that anticipates an artificial virus that can end all life on earth. In the real world, natural selection prevents this from happening. A virus that has no person or creature to infect dies out. A virus needs hosts. There is a natural balance to such things.
In the natural world, in exceptional cases, the cap on virulence loosens temporarily, until the natural balance resumes. In the laboratory of bio-warfare, where hosts can be guaranteed, there is no equivalent cap. A virus is not alive; it is a machine. The only limitation to virulence is the complexity of viral machinery that can be devised to fit in the mechanism that opens the host cell. Some refer to modifications of added capability as gain of function.
What is the limit of virulence? Without the need to preserve some hosts for future infection, is there a limitation to all viral machinery? Is it Ebola or a rabies virus, packaged for airborne delivery? Can stealth aspects be added, as observed with COVID-19 ? What of a constellation of virusoids that co-infect and extend the virulence of the engineered virus?
As a universal killer of all life, the Satan bug is almost impossible. Fiction takes dramatic license. Life fights back with genetic diversity. But the border of reality is unknown. Vaccine technology has made great strides. The methods of trialing a vaccine have not; they do not reflect knowledge at molecular level that was unknown in the whole-virus live-or-killed vaccine era.
This time, the cost in lives of the prolonged vaccine trials will be in the low millions, or tens of millions. It could have been much worse. (Atlantic) Hic sunt dracones. There be dragons.