Chinese officials say another four people have died from a dangerous new strain of bird flu that has now claimed the lives of 31 people.
Central health authorities said late Monday that two of the latest victims were from the eastern province of Jiangsu. The others were from nearby Anhui and Zhejiang.
A total of 129 people, mostly in eastern China, have contracted the H7N9 virus since it was first reported in humans in March. One man in Taiwan has also been diagnosed with the virus, though officials believe he contracted bird flu while traveling in China.
The World Health Organization has called the H7N9 strain one of the most lethal flu viruses ever seen. Unlike other flu viruses that cause upper respiratory problems like coughing and congestion, the new virus attacks the lower part of the lungs, causing high fevers and pneumonia.
Chinese researchers have confirmed that the virus crossed from birds to humans at live markets where chickens and other poultry are slaughtered and sold.
Chinese scientists last month said they feared that H7N9 had transferred in some cases from human to human, which could greatly increase its ability to spread. But the World Health Organization later said there is no evidence this is the case.
China has been working on developing vaccines and other treatments for the H7N9 virus, as part of a wider plan to combat any potential outbreak. It has slaughtered thousands of birds and closed many poultry markets in hopes of slowing the spread of the disease.
This is believed to be the first time humans have contracted the H7N9 bird flu virus. It previously existed only in birds. The more common strain of avian flu, H5N1, has killed more than 360 people worldwide in the last decade.
China is considered one of the countries at greater risk for bird flu because it has the world's biggest poultry population and many chickens in rural areas are raised close to humans.