Chinese officials say four more people have been sickened with a new strain of bird flu, bringing the total of people who have contracted the disease in the country to seven.
The health bureau in the eastern province of Jiangsu said Tuesday that three women and a man had contracted the H7N9 virus, and they are all critically ill.
The bureau said the four cases did not appear connected. It said one of the victims made a living slaughtering poultry, but the others had no such direct contact with birds.
These cases follow reports on Sunday of three other people who became infected with the H7N9 strain, including two men who died in Shanghai early last month. A woman from the province of Anhui is in critical condition after catching the virus.
Before the latest cases were announced, the World Health Organization
said it was investigating the outbreak of H7N9, but that there is no evidence the strain can be transmitted among people.
This is believed the first time that humans have contracted the H7N9 bird flu virus. The more common strain of avian flu, H5N1, has killed more than 360 people worldwide in the last decade.
Most bird flu cases in humans come from close contact with infected poultry. Researchers fear the virus might eventually mutate into a form that is highly contagious among humans.
China is considered one of the countries at higher risk for bird flu because it has the world's largest poultry population, and many chickens in rural areas are kept close to humans.