The new strain of bird flu, H7N9, had spread to two previously uninfected regions over the weekend, after two cases were detected in Henan Province on Sunday and one in Beijing on Saturday.

By 6 pm Sunday, the country had confirmed 60 human infections, up 11 from the previous day, after the virus was first spotted two weeks ago in Shanghai. Shanghai, Zhejiang and Jiangsu reported three, four and two new cases respectively.

The virus also claimed 13 lives across the country by late Sunday, after Shanghai reported two new deaths.

In Beijing's first confirmed case, a 7-year-old girl whose parents work with live poultry has seen her condition stabilize Sunday morning after having been hospitalized for three days. However, a 34-year-old Henan patient with high blood pressure is still in critical condition, some eight days after taking ill.

Nobody who had been in close contact with the newly reported patients in Beijing, Zhejiang and Henan has shown any symptoms, in a sign that the virus is not being transmitted from human to human.

Health experts cited by several media outlets said the virus has been transmitted from East China to Beijing and Henan because birds are migrating northward.

However, Hu Yonghua, dean of the Public Health School at Peking University, told the Global Times that it is now too early to say how the virus has traveled to the north, as the means of transmission remains unknown.

Zhou Zijun, another Peking University professor, said a bird flu outbreak in Beijing is unlikely.

"The bird flu is going to enter a dormant state," he said. "It's getting warm in northern China, and the virus will die out under high temperatures."

The Beijing government has initiated an H7N9 avian flu prevention and control center as well as taking remedial measures including shutting down live poultry markets, bringing in Chinese medicine experts to treat the bird flu and stocking enough of the prevention and treatment medicine, Tamiflu, for 2 million people.

Hu said that closing bird markets is necessary to curb the further transmission of H7N9, as it cuts off the transmission chain of the virus and reduces the risk of an outbreak.

However, Huang Kai, a Chinese medicine expert with the Hunan-based LBX Pharmacy, told the Global Times that closing the markets is only a short-term solution.

"Live poultry trading is a huge business," Huang said. "When better prevention and treatment measures such as vaccines are found, the markets should be reopened."

Both Hu and Huang said live poultry markets need close supervision.