Whoa, some viruses may pass from one species to another. Not all are species specific. Rabies is one of them. It is speculated that HIV is another. Bovine spongioform encephalitis (whatever causes it) passed from sheep to cows to humans. Who has studies the 100 or so viruses that cause colds in humans and knows that they cannot be transferred to dogs or other animals? By the way, if something passed from cows to humans, shouldn't we be a little concerned about feeding so many of our children on milk from these animals? Jack Newman, MD, FRCPC