Any time there is some sort of illness in a snake it is usually assumed to be paramixo virus. That is one of the few viruses that we know of that can effect reptiles but when you think of how many viruses humans or cat and dogs can get and compare it to the measly 2 or 3 known viruses in snakes you will see that there is a lot that we do not know. I am willing to bet that there are hundreds if not thousands of viruses out there that we do not know about that can affect snakes. This will be an interesting area to watch now that it is finally being studied a little bit.
As a side note, I have 3 old books on reptile husbandry that mention something called SSDS or Sudden Serpent Death Syndrome which was the unexpected death that occurred seemingly for no reason. None of them agree on the symptoms. I wonder how many snakes died from other viruses like this one that have been labeled as SSDS.