GUANGZHOU - A human infection with the H7N9 strain of avian influenza was confirmed in South China's Guangdong province, Guangdong's health department said Saturday.

Sample of a 51-year-old woman tested positive for the H7N9 virus at the Chinese Center for Disease Control and Prevention on Saturday, confirming the results of tests conducted by the Guangdong provincial center for disease control and prevention on Friday, the department said in a statement.

The infected patient, surnamed Chen, was admitted to Huizhou City Central People's Hospital on August 3 after having a fever for one week. She has been a poultry slaughtering worker at a local marketplace for many years in Boluo County.

She was transferred to the First Affiliated Hospital of Guangzhou Medical University for treatment on Friday night.

The patient is in critical condition but remains conscious with stable life sign parameters, the department said.

Zhong Nanshan, director of the Guangzhou Institute of Respiratory Diseases, has drawn up a treatment plan for Chen. An expert team has also been set up to treat the patient.

As of 4 pm Saturday, local health authorities have lifted medical observation for 54 out of 96 people who were placed under medical monitoring after they had close contact with the patient.

The patient's son showed a low fever on Friday night with his body temperature hitting 37.8 degrees Celsius, according to the Guangdong Provincial Center for Disease Control and Prevention.

But he tested H7N9 negative and his fever disappeared in the early hours on Saturday, said the center.

The other people who had close contact with the woman have shown no abnormal symptoms so far.

Liao Xinbo, deputy director of the Guangdong Provincial Health Department, said after an epidemic survey, Guangdong still faces the risk of sporadic human H7N9 infections and the possibility of human-to-human infection could not be ruled out.

After Chen was diagnosed as a suspected H7N9 infection case, agricultural authorities conducted tests on samples of all poultry including 69 chickens, eight ducks and one goose at the marketplace where Chen had worked, said an official with the Guangdong provincial agriculture department.

All samples, including 25 environmental samples,tested negative for the H7 viruses, said the official.

The new case in Guangdong brought the total of human H7N9 infections on the Chinese mainland to 134 this year. Of the cases, 44 have died. In July, China reported a single H7N9 avian flu case from the northern province of Hebei.

Coincidentally, after studying two human H7N9 cases diagnosed in east China's Jiangsu Province, researchers with the Jiangsu Provincial Center for Disease Prevention and Control said earlier this month that the H7N9 virus may have spread from human to human but the transmission was limited and non-sustainable.

The two infected with H7N9 in Jiangsu were a father and his daughter, who were both killed by H7N9 in April.

Researchers concluded in a report posted on the website of the British Medical Journal on Wednesday that it is very likely that the H7N9 bird flu was "transmitted directly from the 60-year-old father to his daughter."

China stopped the emergency response to the H7N9 avian flu outbreak in late May.

But the country has been monitoring the situation and is preparing for any possible outbreaks in the coming autumn and winter, said Deng Haihua, spokesman for the National Health and Family Planning Commission, on Thursday.