This newly discovered thousands of years old virus was able to infect modern day amoebas. Yes, we share a lot of cell wall proteins with pigs and chickens and ferrets. Influenza jumps between multiple species: horses to dogs, wild birds to zoo cats, ducks to people back to pigs and on to chickens. SARS jumped to people from civet cats and a new strain in the same virus family is currently infecting humans and camels. So species jumping isn't such a rare event. Once a virus enters a host and starts making copies, the mutations occur and the chance for some of those mutations to more efficiently infect that same host occurs. I know what you are saying and it is true, people misunderstand what the actual risk of a new pathogen causing a pandemic are. The potential for humans unleashing a new viral pathogen occur with the bushmeat trade in Africa, the further intrusion into the Amazon Rain Forest, and within human populations that live in close contact with domestic animals. The 2009 H1N1 flu virus that caused recent problems likely emerged in a pig farm in Mexico. My point is that the thawing tundra is yet another place where humans can potentially encounter new pathogens.
Off-topic for just a minute: A member made it very clear to me that deep offense was taken to language I used yesterday in my frustration with the behavior in this thread. The member is perfectly correct and had every reason to be offended. My language was well beyond the pale. I apologies to any and all who were offended at the statement, which constitutes an act.