I interpreted the poster to be referring to some sort of primitive organism that might out evolve humans, but I suppose an existing pathogenic organism could enter the gradations of evolution and become a super bug that wipes out humanity.
I think humans are very smart, also are the immune response to diseases. I only believe pathogens will only reduce human population, but there will be some that will not die of pathogens. What I think can lead to extinction of humans is if what is powering the Earth is no longer existing, or if the Earth in any other way become inhabitable.
I never did any research about the causes of the Covid-19 and other viruses but if you read what I said earlier, I said it is always a product of human mistakes but when it happens it will come out of the blue and there's always something that triggers it.
Covid-19 can be because of research mistake in China, but no one knows, it can also be because of natural changes in Corona virus that makes it more deadly than before. Everything can not be because of human mistakes, some just evolved naturally. One thing about microbes is that they can naturally genetically modified with short period of time.
How can that be when humans are scared of animals. Man lost that glory of superiority when he lost out to the devil in the garden of Eden by disobeying God. Whatever man does now will not prove him in anyway superior.
At the dawn of human evolution, how did you know that humans are not scared of some animals but having the intelligence that made then superior.