I'm not disputing the facts in this post, about Europeans exposing natives to strains of agressive viruses that they had no defenses to. Or washing hands being a great way to reduce your risk. Just the whole conclusion you draw about viruses in general existing in the new world.
Here is a compilation of what modern science has to say about the origins of viruses on this little ball we call Earth.
Viruses are found wherever there is life and have probably existed since living cells first evolved.
The origin of viruses is unclear because they do not form fossils, so molecular techniques have been the most useful means of investigating how they arose. These techniques rely on the availability of ancient viral DNA or RNA, but, unfortunately, most of the viruses that have been preserved and stored in laboratories are less than 90 years old.
There are three main theories of the origins of viruses:
Regressive theory: Viruses may have once been small cells that parasitised larger cells. Over time, genes not required by their parasitism were lost. This is also called the degeneracy theory.
Cellular origin theory (sometimes called the vagrancy theory): Some viruses may have evolved from bits of DNA or RNA that "escaped" from the genes of a larger organism.
Coevolution theory: Viruses may have evolved from complex molecules of protein and nucleic acid at the same time as cells first appeared on earth and would have been dependent on cellular life for many millions of years.
I agree that many viruses arose from all the means you mentioned however you have left out many many types of viruses that didn't originate from those sources like for example the viruses in apes and monkeys (I think there were a few monkey species in the new world like say in the
Amazon basin maybe or the jungles of Central America). It is very possible that whole groups of ancient human populations died off from prehistoric viral infections that crossed species from monkey to man.