Of the 13 cases contracted in the city of Beijing itself, six people have died, six were cured and one is undergoing medical treatment, Pang Xinghuo, deputy director of the center, said at a news conference.

Most of the other cases were contracted in areas neighboring Beijing. Of those, 11 were cured and three are undergoing treatment, he said.

The center said no apparent mutation has been detected in the virus and no human-to-human transmission of the disease has been reported in Beijing, so the public need not panic.

"The number of H7N9 cases in China is higher than usual, and Beijing is no exception," Mr Pang said. "The people were infected through poultry, but there have been no concentrated outbreaks in Beijing."

China saw its biggest H7N9 outbreak over the past winter since the virus was first reported in China in 2013. A total of 352 human cases of H7N9 were reported in the first two months of this year, with 140 deaths, according to the National Health and Family Planning Commission. By comparison, 57 cases were reported in the first two months of 2016, the commission said.

Twelve H7N9 cases were reported between 2 and 8 June in nine provincial regions in China, and the number of new cases remained low for three consecutive weeks, the commission said last month. There is no evidence that the virus is becoming more infectious to humans, it said.

The Ministry of Agriculture announced in June that South China's Guangdong province and the Guangxi Zhuang autonomous region - two major centers for the poultry trade in China - had been chosen as pilot regions where all chickens, ducks and geese will receive vaccines against the H7N9 virus. Veterinary authorities of the two regions may start administering vaccinations in July, monitor the side effects and report the findings to the ministry, it said.

The Beijing Center for Disease Prevention and Control said residents should continue to take precautionary measures to prevent infection, such as avoiding contact with live poultry and cooking eggs and meat thoroughly, even though the disease is less likely to show up in summer.

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