Can the deadly Ebola virus disease infect animals? And can those animals spread it to humans? A dog whose owner was infected with the virus was euthanized in Spain last week because of that possibility.

Experts said they don't have all of the answers yet, but some animals can get the virus. It's more complicated than that, though, because animals don't show the symptoms.

So, can the virus then be spread to humans? Maybe.

Ebola has been detected in monkeys, bats, pigs, horses and dogs. But there is a big difference between carrying the virus and transmitting it.

"While, yes, they can contract the virus — whether they carry the virus and can spread it to animals or other people is still unclear," said Dr. Kristen Olsen, an internal medicine specialist at Affiliated Veterinary Specialists.

But knowing if an animal has the Ebola virus is even harder to tell.

"They never would show an outward sign that they have the infection," Olsen said.

In primates and humans, the symptoms can't be ignored.

"Consistently, it's going to be fever, diarrhea, vomiting and, in more severe cases, abnormal bleeding," said Dr. Timothy Hendrix, of CentraCare.

But it could take as many as 21 days before those symptoms take over. So in that incubation period, any physical contact could spread the virus. And that is what is causing concern about potentially infected animals, like dogs.

"So theoretically, if they ever prove that the virus is carried in saliva of dogs, then yes, that may be some type of possibility," Olsen said.

Medical experts said there are very few diseases that can be transmitted from animals to humans. It will take more time to study the virus to get those answers, experts said.

The Centers for Disease Control and Prevention said there have been no reports of pet dogs or cats becoming sick with Ebola or passing the disease on to other animals or people in the U.S. They said they are working with the American Veterinary Medical Association to develop a plan for the pet population in the United States.