Tourists who took their pets along when they visited a wildlife center in Shaanxi may have spread the canine distemper virus that killed four giant pandas, according to National People's Congress deputy Hou Rong.

"Experts are still looking for the source of the virus, and I think pets are a possibility," said Hou, the head of the Chengdu Research Base of Giant Panda Breeding in Sichuan province.

"Some tourists have hidden their dogs or cats in bags and brought them into our panda base. Though this is prohibited and there are 'no pets' signs everywhere, people still do it."

Canine distemper is a highly contagious virus that mainly affects dogs and cats and has a mortality rate of up to 80 percent.

The pandas that died were at the Shaanxi Rare Wildlife Rescue and Breeding Research Center in Xi'an, the capital of Shaanxi province. The first animal died on December 9, and the most recent death occurred at the beginning of February.

Another panda became infected and three more displayed symptoms, but all four survived.

Hou, speaking at the NPC's annual session, said no cases of canine distemper have been found at the panda base in Sichuan. However, she feels the conduct of tourists should be regulated.

"At a zoo in Nanjing, a giraffe had a nervous breakdown because of the loud music played by people who went there and danced," she said. "Giraffes are very sensitive animals and have evolved to live in a quiet environment.

"People are not supposed to feed the animals. However, after every holiday, zoos often find dead monkeys that have eaten too much."

An amendment to the law covering wildlife conservation was on the agenda of the NPC session, and consequently Hou feels this is the perfect time to introduce legislation regulating the behavior of tourists.

"If we don't have laws, we have no power to stop people from harming animals," she said.

She gave the case of Liu Haiyang, a student at Beijing's Tsinghua University, as an example of the sort of behavior that should be outlawed.

In 2002, Liu took acid to Beijing Zoo and threw it onto bears, causing burn wounds. Liu was accused by prosecutors of destroying public property, but escaped without penalty because the court ruled that the damage was minor.