The coronavirus has infected two cats in New York state, making them the first pets to test positive for the virus in the U.S., the Centers for Disease Control and Prevention said on Wednesday.

One of the cats was tested after it showed mild respiratory signs, although its owners were not confirmed to have Covid-19. The virus may have been transmitted to this cat by mildly ill or asymptomatic household members or through contact with an infected person outside its home, the CDC said.

The owner of the second cat had tested positive for the coronavirus, and the animal was also tested after showing signs of respiratory illness.

The two cats live in separate areas of the state and are expected to make a full recovery, the CDC said. The department said routine testing of animals is not recommended at this time and state animal health and public health officials will take the lead in making determinations about whether animals should be tested.

There's currently no evidence that pets play a role in spreading the virus. Further studies are needed to understand if and how different animals, including pets, could be affected, the CDC said.

On Wednesday, the Bronx Zoo announced in a statement that an additional three tigers and three lions have tested positive. The zoo previously announced on April 5 that a 4-year-old tiger at the zoo named Nadia tested positive for COVID-19 after developing a dry cough.

World Health Organization officials said they're investigating several cases where pets appear to have been infected with the coronavirus by their human caretakers.

One study conducted on cats in Wuhan found that the pets could be infected with the coronavirus, Dr. Maria Van Kerkhove, the WHO's technical lead on the outbreak, said during a recent press conference. She added that world health officials don't believe the animals are playing a role in transmission to humans, although humans can infect animals.

It's "really important we remain respectful and kind" to the animals that are likely to be co-infected with humans, Dr. Mike Ryan, executive director of the WHO's health emergencies program, said at the press conference.

"They're beings in their own right, and they deserve to be treated with kindness and respect," Ryan said. "They're victims like the rest of us."