Another panda bear has died after contracting canine distemper virus (CDV), the fifth in four months in a Shaanxi-based wildlife center, an official with the center told the Global Times Thursday.

The fifth panda, 5-year-old Long Long, died on Wednesday after being treated for three months. Long Long was the only male among the five dead pandas since the first death in December, according to Han Xueli, director of the publicity office at the Shaanxi rescue, breeding and research center for rare wild animals.

"The other 20 pandas are healthy and have been sent to other nature reserves in the province," Han told the Global Times.

Han said that the healthy pandas would be returned after a sanitary assessment is completed by panda experts and veterinarians.

While the exact reason for the infection remains unclear, panda experts have questioned the center's location and disease prevention measures.

The center was built on the north side of Qinling Mountain in 1987.

Pandas have special living requirements, such as high humidity, low temperatures and a high altitude. But the center is dry, densely populated and has no bamboo anywhere near the area, said Diao Kunpeng, a panda expert with the NGO Shan Shui Conservation Center (SSCC) devoted to promoting biodiversity in China.

The required living environment of pandas can be found only in the south of Qinling Mountain in Shaanxi Province, Diao said.

"More importantly, the center is in a scenic spot surrounded by hotels and residential compounds with many pet animals, which have posed health risks to pandas," Diao told the Global Times.

The center is located more than 80 kilometers southwest of Xi'an, the capital of Shaanxi.

Huang Yan, deputy chief engineer of the Sichuan-based China Conservation and Research Center for the Giant Panda (CCRCGP), also believes that the center's location increases the risk of infections through contact with other animals and people.

The center is open to the public and charges an entry fee for a tour of over 20 kinds of rare animals, such as pandas, takins and snub-nosed monkeys.

CDV is a highly contagious disease quite common among a variety of animals including dogs, mice and bats. The infected animals usually have high fever, bouts of coughing, vomiting and diarrhea. It is spread through contact with infected body fluids or contaminated food and water.

"But the disease is deadly once transmitted to pandas, and there is no cure at this stage," Diao said.

The current vaccines can prevent most animals from being infected with the virus, but there are no vaccines available for pandas, Diao added.

Han admitted that the center is densely populated with nearby villagers keeping cats and dogs, but he claimed that the center bans pet animals.

Han declined to comment on the possible health risks posed by the center's location, but said panda experts are still investigating.

According to Han, all the pandas at the center are kept in captivity, and each has its own room with air conditioning facilities.

"The key to protecting captive pandas lies in effective disease prevention measures," Huang said.

The CCRCGP strictly bans any pet animals at the center, prohibits visitors from coming in  contact with the pandas and bans breeders from keeping any pets, Huang said.

According to the fourth national giant panda survey revealed in February, there were 1,864 wild pandas in China as of 2013. Most of the 345 wild pandas found in Shaanxi are found in the south side of the Qinling Mountain. There are also 375 living in captivity.

The State Forestry Administration will draft a giant panda protection regulation to protect the habitat of the endangered animal, news portal thepaper.cn reported on Thursday.