Two people in the central Chinese province of Henan have been infected by a new strain of avian influenza bringing the nationwide total to 51, state media have reported.
The latest cases of infections from the H7N9 bird flu virus, reported on Sunday, were the first in the province.
One of the victims, a 34-year old man in the city of Kaifeng, is critically ill in hospital, while the other, a 65-year old farmer from Zhoukou, is stable. The two cases do not appear to be connected.
A total of 19 people in close contact with the two victims were under observation but had shown no signs of infection, said Xinhua news agency said.
On Saturday, Xinua reported that a seven-year-old girl in the capital city of Beijing was the first person to contract bird flu outside of the eastern region.
The girl was reportedly in a stable condition in a Beijing hospital, and was given the drug Tamiflu, received intravenous drips on Thursday night, and was transferred to an intensive care unit when her condition worsened.
The parents of the girl, who developed flu symptoms on Thursday morning, are engaged in the live poultry trade.
Michael O'Leary, head of the World Health Organisation's office in China, said that members of the organisation were not surprised that the virus had spread, and they "still expect that there will be other cases."
So far 11 people have died of the H7N9 bird flu strain since it was confirmed in humans for the first time last month.
Shanghai and the eastern provinces of Zhejiang, Jiangsu and Anhui had been the only confirmed locations of infection until the case in Beijing, a city home to over 20 million people, and Sunday's report from Henan.
The source of infection remains unknown, though the virus has been found in some birds in poultry markets that remain the focus of investigations by China and the UN Food and Agriculture Organisation.
The new virus has caused severe illness in most of the people affected, leading to fears that if it becomes easily transmissible, it could cause a deadly influenza pandemic, though there has been no indication of that happening.
In a bid to calm public jitters over the virus, Chinese authorities have detained a dozen people for spreading rumours about the spread of bird flu.
Earlier in April, the World Health Organisation praised China for mobilising resources nationwide to combat the strain by culling tens of thousands of birds and monitoring hundreds of people close to those infected.
"So far, we really only have sporadic cases of a rare disease, and perhaps it will remain that way. So this is not a time for over-reaction or panic," said Michael O'Leary, the WHO's representative to China.