Nadia, a four-year-old female Malayan tiger at the Bronx Zoo, has become the first tiger in the world to test positive for the coronavirus. It is the first known case of an animal contracting the coronavirus in the United States. Nadia’s sister Azul, two Amur tigers, and three African lions have also developed a dry cough, a symptom that is typical of COVID-19 patients. Because of the difficulty of obtaining samples from big cats, only one was tested. Besides a bit of loss of appetite all the Bronx Zoo animals are doing well, the Wildlife Conservation Society’s Bronx Zoo said in a statement. The zoo has been closed since March 16.

The U.S. Department of Agriculture confirmed the finding and said it marked the first case of a tiger testing positive for COVID-19. The big cats were likely infected by an asymptomatic staff member.

Even though all the big cats infected with COVID-19 are expected to make a full recovery the positive test raises fresh questions about how the virus is transmitted to animals. No pets in the United States have tested positive for the virus and there is no evidence to suggest that animals can transmit COVID-19 to people. A dog in Hong Kong tested positive, which led officials to conclude animals could test positive if they had been exposed by humans but could not transmit the virus to humans.

The USDA says anyone who is sick with the coronavirus should restrict contact with animals as much as possible. If someone who is sick with the coronavirus must take care of a pet or be around animals, “they should wash their hands before and after the interaction,” notes the USDA. Experts also recommend that pets of owners who are infected with COVID-19 should be kept inside as much as possible.