Forty-seven tigers, three lions and a panther have died in zoos in south Vietnam due to the H5N1 bird flu virus, state media said Wednesday.

The deaths occurred in August and September at the private My Quynh safari park in Long An province and the Vuon Xoai zoo in Dong Nai, near Ho Chi Minh City, the official Vietnam News Agency (VNA) reported.

According to test results from the National Centre for Animal Health Diagnosis, the animals died “because of H5N1 type A virus,” VNA said.

The zoos declined to comment when contacted by AFP.

No zoo staff members in close contact with the animals had experienced respiratory symptoms, the VNA report added.

Education for Nature Vietnam, an NGO that focuses on wildlife conservation, said there were a total of 385 tigers living in captivity in Vietnam at the end of 2023.

About 310 are kept at 16 privately owned farms and zoos, while the rest are in state-owned facilities.

The World Health Organization says that since 2022, there have been increasing reports of deadly outbreaks among mammals caused by influenza viruses, including H5N1.

It also says H5N1 infections can range from mild to severe in humans, and in some cases can even be fatal.

Vietnam notified the WHO about a human fatality from the virus in March.

In 2004, dozens of tigers died from bird flu or were culled at the world’s largest breeding farm in Thailand.

In the U.S., bird flu has been detected in about 200 dairy herds in 14 states this year, according to the U.S. Department of Agriculture. Bird flu has also been found in commercial and backyard flocks and in wild birds.

Last month, health officials in Missouri said a hospitalized patient was infected with bird flu despite having had no known contact with dairy cows or other animals associated with an ongoing outbreak. At the time, It marked the 14th person in the U.S. sickened with bird flu since March, when the virus was detected in cows, after infecting wild birds and mammals worldwide.

The CDC says it is using flu surveillance systems to monitor for bird flu activity in people.