Giant panda twins Maozhu and Maosun play at the Giant Panda Research Base in Chengdu, Sichuan province. A virus outbreak has claimed the lives of two pandas and left a third one in critical condition. Reuters

Another giant panda in China is fighting for its life as it battles a highly infectious virus that has already claimed the lives of two others. Medical tests on the 5-year-old panda Feng Feng showed serious heart, liver, kidney and lung damage from the virus, and veterinarians are providing antiviral treatments to keep Feng Feng’s condition stable, according to Chinese state media.

"It's hard on giant pandas, because no companies or research institutions at home produce vaccines that are specially designed for giant pandas. In other words, we can hardly find a vaccine that can give effective protection," Jin Yipeng, associate professor of veterinary medicine at China Agriculture University, told China’s state media CCTV, according to CNN.

Feng Feng has been identified to be afflicted with the canine distemper virus (CDV), a highly contagious and fatal disease, a spokesman for the Shaanxi provincial wildlife rescue, breeding and research center told Chinese news Xinhua. Feng Feng was diagnosed with the virus on Dec. 26 and began to show neurological symptoms on Jan. 2.

The virus has an 80 percent fatality rate for pandas. CDV can also affect dogs, primates and large cats, and it targets the gastrointestinal and respiratory tract, the spinal cord and the brain. Symptoms include high fever, eye inflammation, coughing, vomiting, diarrhea and lethargy. The virus commonly spreads via infected body fluids or contaminated food and water.

Two other pandas have fallen to the CDV. Da Bao, an 8-year-old panda, died from heart failure and lung edema from the virus on Jan. 4. Another 8-year-old panda Cheng Cheng died on Dec. 9, according to Xinhua. Panda breeding centers in the neighboring Sichuan province have instituted emergency measures, including enhanced disinfection of panda enclosures and limits on public contact, according to CNN.

Giant pandas are considered an incredibly endangered species, and China, which considers pandas one of its national treasures, has spent considerable resources to try to preserve them. Scientists have made recent breakthroughs in successfully getting pandas to breed in captivity, and a virus outbreak could undermine those efforts.