It's gonna come sooner rather than later. Humans encroach on the natural habitats of animals all over the world, which increases the number zoonoses dramatically. Most such spillovers don't cause any further human to human spread. Think of MERS. But there are spillovers that do spread between humans, like in the case of SARS-Cov-2. While the COVID pandemic is a major catastrophy, we were still quite lucky. MERS has a much higher case fatality ratio. Something that spreads as easily as SARS-Cov-2 while being as deadly as MERS is entirely possible.

We should start preparing once most of the population is vaccinated and human societies have returned to normal. Develop and test antivirals targetting the conserved proteins in major virus families. Build a pipeline that can respond to new viruses quickly with a vaccine. Create capacities to quickly ramp up mass production of PPE. Map the viruses that appear in animals around us to know what we are up to.

I hope that political leaders will listen to the people doing such proposals.