The virus, previously not thought to infect snakes at all, appears to cause "inclusion body disease." Long the bane of zoo officials and exotic pet owners, the deadly illness spreads among boas and pythons in captivity, causing micro clumps of clustered proteins to form inside the snake, leading to bacterial infections, neurological problems, anorexia and withering, leading to death.

Surprisingly, he said, the cause of the illness appears to be a completely new set of viruses of a type known as an arenavirus. The discovery came as a complete a shock to the team of scientists because, while arenaviruses are common in rodents and cause extremely nasty infections in other mammals, nobody knew they could infect reptiles.

Arenaviruses infect mostly rodents but occasionally people, and can cause fatal hemorrhagic diseases like Lassa fever, which kills thousands of people every year in Africa. There is no evidence, however, that a snake has ever transmitted an arenavirus infection to a person despite the fact that snake owners and veterinarians handle infected snakes all the time, said DeRisi.

The team found two arenavirus strains in the snakes -- a surprise in itself; but in addition, they observed that the viruses did not look like your ordinary arenaviruses. They looked like distant relatives of other arenaviruses but had protein coats that were more similar to those of Ebola viruses. Like arenaviruses, Ebola virus can cause fatal hemorrhagic fever when transmitted to humans. Neither of those viruses has ever been known to infect reptiles, and although it had been postulated that they share a common ancestor, no such virus linking them had ever been discovered.