It seems like viruses always tread a spectrum between infectivity and lethality. Does or could a virus exist which: - has a 100% fatality rate, like rabies -

It seems like viruses always tread a spectrum between infectivity and lethality. Does or could a virus exist which: - has a 100% fatality rate, like rabies - can keep the host alive long enough to spread and - cannot be defeated by any prospective vaccine or can evolve fast enough to evade them? Basically, airborne and human-to-human rabies, with no vaccine. Or vaccine resistant ebola, but even more lethal, infectious, and a longer incubation period. Put more concisely, could a virus exist with the potential to wipe us out.