peter cowen is an associate professor of epidemiology at north carolina state's college of veterinary medicine. he has advised the cdc and world health organization on transmission of diseases from animals and the cdc itself tweeted it's working to develop guidance for the u.s. pet population. dr. cowen, did x caliber have to die? >> there has never been a known transmission from dogs to humans of the ebola virus. so we really could have learned a lot by, you know, trying to move in another direction with this animal. >> why couldn't the dog be quarantined, like understand is the case with the husband of the nurse in spain who tested positive? >> we needed to learn whether that woman had transmitted ebola to the dog before we even know the next question, which is can the dog then transmit it to others. so once the dog is euthanized, we never get an answer to that. and we really need answers to these questions. you know, when we study the ebola virus, we study it mainly in humans, and we do a little bit of work in wildlife to find out that bats and other chimpanzees and other animals a