A poultry worker was confirmed as having contracted the deadly H7N9 bird flu virus, health officials said, the first case in the southern Guangdong province as nearby Hong Kong remained on alert.
The 51-year-old woman is in critical condition after she was admitted to hospital on August 3 following signs of a fever, the Guangdong Provincial Health Department said on Saturday.
“She was a poultry slaughtering worker at a local marketplace,” the local health bureau said in a statement on its website.
A total of 134 cases have now been reported on the Chinese mainland, including the Guangdong case. A Hong Kong government spokesman said on Sunday that it was closely monitoring the virus for any developments.
Hong Kong Centre for Health Protection controller Dr Leung Ting-hung has said  earlier that the city might see its first infection in the next few months if the Guangdong case was confirmed. "After all, cross-border activities are so frequent; we should be prepared for that."
"We should be mindful of the situation, as Guangdong is adjacent to Hong Kong," Leung said. "We are also paying attention to whether the virus has been changing or has the ability to spread from human to human."
State news agency Xinhua said on Saturday that 44 people had died of the disease – which includes a recent fatality following the release of the latest official figures a month ago.
The virus was first reported in late March, with most cases confined to eastern China, and only one reported outside the mainland, in Taiwan.
Scientists reported last week the first likely case of direct person-to-person transmission of the H7N9.
However, they told people to “not panic” as the virus’s transmissibility remained “limited and non-sustainable”.
Local health authorities on Saturday lifted medical observations on 54 of 96 people who were placed under monitoring after they had close contact with the Guangdong patient, Xinhua said.
The patient had worked in markets in Boluo, which is about 129 kilometres east of the provincial capital Guangzhou.
Many of those infected with the virus had direct contact with birds, commonly at poultry markets, which have been closed by officials across China to halt the spread of the disease.
Cases of H7N9 have dropped significantly in recent weeks.
View H7N9 map  in a larger map
Click on each balloon for more information on individual patients infected: blue, patients infected with the H7N9 virus under treatment; red, those infected with H7N9 who have died; yellow, those who have fully recovered; and pink, those infected other types of the Influenza A virus, including H1N1.