As experts in Ohio are studying a number of dog deaths and the possibility that a novel virus is involved, veterinarians are fielding calls from concerned owners and telling people to be cautious but not panic. Circovirus, a pathogen only recently identified in dogs, was found in a fecal sample from one dog, but biological samples from two dogs in different parts of the state tested negative. However, experts cautioned that very little is known about circovirus in dogs. "There is no way of saying 'This dog is positive, this dog is negative' yet with circovirus because we don't know the best tissue to sample," said veterinarian Patricia Pesavento of the University of California, Davis. And Ohio state veterinarian Tony Forshey noted it's not even clear whether circovirus was the cause of illness in the animals that tested positive.