The Shanghai Zoo said on Monday that it has stepped up epidemic prevention efforts after a tiger in the US tested positive for the respiratory disease caused by COVID-19 on Sunday.

Nadia, a 4-year-old female Malayan tiger at the Bronx Zoo in New York City, became the first animal known to be infected with the virus in the US after it was tested on April 2. Nadia had developed a dry cough in late March.

Six other big cats at the zoo – three tigers and three lions – have also exhibited symptoms of the illness, according to the US Department of Agriculture.

In light of this incident, a Shanghai Zoo spokesperson said that the park has increased its disinfection frequency and instructed staff to ensure that visitors do not feed the animals or litter within the premises. The zoo also required all staff members and visitors have to wear masks when in the park.

The Shanghai Zoo reopened its doors to the public on March 13, with visitor numbers totaling 11,738 on Sunday.