China's H7N9 bird flu virus spread to a new province on Sunday, with state media reporting two human cases in central Henan just west of the area where the disease has been centred.
Until Saturday, when one case was reported in the capital of Beijing, all other instances had occurred in the eastern city of Shanghai and nearby Zhejiang, Jiangsu and Anhui provinces hundreds of kilometres away reports AAP.
Altogether 51 people have been infected and 11 have died of the disease since Chinese authorities announced two weeks ago they had found H7N9 in humans for the first time.
Experts fear the prospect of such viruses mutating into a form easily transmissible between humans, which would have the potential to trigger a pandemic.
But the World Health Organisation said last week there was as yet no evidence of human-to-human transmission of H7N9.
Health authorities in China say they do not know exactly how the virus is spreading, but it is believed to be crossing from birds to humans, prompting mass poultry culls in several cities.
The United Nations' Food and Agriculture Organisation has said H7N9 shows "affinity" to humans while causing "very mild or no disease" in infected poultry, making it more difficult to find the source of transmission.
