HANOI, Vietnam (AP) — More than a dozen tigers were incinerated after the animals contracted bird flu at a zoo in southern Vietnam, officials said.

State media VNExpress cited a caretaker at Vuon Xoai zoo in Bien Hoa city saying the animals were fed with raw chicken bought from nearby farms. The panther and 20 tigers, including several cubs, weighed between 10 and 120 kilograms (20 and 265 pounds) when they died. The bodies were incinerated and buried on the premises.

“The tigers died so fast. They looked weak, refused to eat and died after two days of falling sick,” said zoo manager Nguyen Ba Phuc.

Samples taken from the tigers tested positive for H5N1, the virus that causes bird flu.

The virus was first identified in 1959 and grew into a widespread and highly lethal menace to migratory birds and domesticated poultry. It has since evolved, and in recent years H5N1 was detected in a growing number of animals ranging from dogs and cats to sea lions and polar bears.

In cats, scientists have found the virus attacking the brain, damaging and clotting blood vessels and causing seizures and death.

More than 20 other tigers were isolated for monitoring. The zoo houses some 3,000 other animals including lions, bears, rhinos, hippos and giraffes.

The 30 staff members who were taking care of the tigers tested negative for bird flu and were in normal health condition, VNExpress reported. Another outbreak also occurred at a zoo in nearby Long An province, where 27 tigers and 3 lions died within a week in September, the newspaper said.

Unusual flu strains that come from animals are occasionally found in people. Health officials in the United States said Thursday that two dairy workers in California were infected — making 16 total cases detected in the country in 2024.

“The deaths of 47 tigers, three lions, and a panther at My Quynh Safari and Vuon Xoai Zoo amid Vietnam’s bird flu outbreak are tragic and highlight the risks of keeping wild animals in captivity,” PETA Senior Vice President Jason Baker said in a statement sent to The Associated Press.

“The exploitation of wild animals also puts global human health at risk by increasing the likelihood of another pandemic,” Baker said.

Bird flu has caused hundreds of deaths around the world, the vast majority of them involving direct contact between people and infected birds.