The risk of natural pandemics threatening civilization is at most .1%

The Wildfire scenario requires the introduction of a lethal pandemic agent capable of spreading through populations of essential workers in every nation, even after they adjust their workflows to minimise human contact. The Omicron variant of SARS-CoV-2 plausibly sufficed. Drawing from data on its spread in previously naive Chinese populations in the months before and just after the relaxation of that country's zero-COVID policy, Omicron likely exhibits an R0 between 4.0 and 5.5 with an upper bound of 6.8 (see Appendix 1). We therefore define a Wildfire pathogen as one exhibiting a case fatality rate above 20% and a basic reproduction number exceeding 5.5. Only one pandemic pathogen in the four thousand years in which densely populated cities and frequently used trade routes have been key features of civilisation,22 i.e. the variola major virus that causes smallpox, has been both highly lethal (~30% case fatality rate) and could be sufficiently contagious (R0=3.5-6.0).23 Therefore, historical inference suggests that the annual chance of a natural Wildfire pandemic is somewhere between negligible and a theoretical maximum of 0.1% (see Appendix 1).