Of course, it's also possible that by the point genetic engineering is sufficiently well understood and accessible to the public that someone could create a doo

Of course, it's also possible that by the point genetic engineering is sufficiently well understood and accessible to the public that someone could create a doomsday plague in their garage we'll have medical technology sufficient to deal with the threat. We've sort of followed that trajectory with computer viruses, after all. This still doesn't say good things about the survivability of the 3rd world, though. Even though modern server, desktop and handheld devices (let's call these "people with high-tier healthcare") are rather well hardened, older systems (people without that healthcare) and IoT devices (pets/farm animals/crops/nature) are notoriously vulnerable.