Shanghai yesterday announced its third serious case of?A/H1N1 flu - a 43-year-old man who was in stable condition at the Shanghai Public Health Clinical Center.

The patient, a local resident, was being treated last night in a negative-pressure ward that specializes in victims of the A/H1N1 virus. He was receiving oxygen but was conscious.

The patient was confirmed as a serious case of?A/H1N1 flu on Monday and transferred from the Jiading District Central Hospital to the clinical center that night.

Dr Lu Shuihua, director of respiratory disease at the center, said the patient had a severe cough, rapid breathing and a large lung shadow indicating a pulmonary infection. The patient also suffers from pre-existing hypertension.

"After a day of treatment, his condition has stabilized and it shouldn't deteriorate," Lu said. "However, he still suffers multi-viral infections in his lungs and injury to his heart muscle."

As of noon last Thursday, the city had detected 1,538 cases of?A/H1N1 flu since the first was reported in May. The other two serious cases have recovered.

Shanghai Health Bureau officials said the number of patients at local fever clinics has not grown significantly in recent days and the incidence of?A/H1N1 flu has remained stable.

But they expect an increase in serious cases of swine flu due to the spread of the virus.

"Higher-risk groups including obese people, pregnant women and those with serious diseases who experience flu-like symptoms should go to the hospital as soon as they feel sick," said Dr Yuan Zhenghong of the Shanghai Public Health Clinical Center.

The Shanghai Health Bureau yesterday ordered 136 hospital fever clinics to enhance supervision of patients with unknown forms of pneumonia and to screen for?A/H1N1 flu, SARS and avian influenza.

People suspected of having those diseases must be reported immediately and samples sent for laboratory tests for early detection and treatment. To prepare for a second wave of swine flu, the health bureau is requiring schools to tighten morning checks and supervision of illness detection.