A new bird flu test will be conducted in the city’s wet markets in an attempt to tighten surveillance of the virus amid a spike in human infections in mainland China.

The number of human cases of H7 on the mainland this winter had reached 364 by Tuesday. That surpassed the usual 200 or so cases reported in the past few years, Dr Wong Ka-hing, controller of the Centre for Health Protection in Hong Kong, said on Wednesday.

Four human cases, including two fatalities, have been reported in the city so far – all had travelled to the mainland.

“The peak of this wave has become more severe than in the past and the health authority remains very concerned about the situation,” Wong said.

“Since many of these human cases took place in Guangdong, neighbouring Hong Kong, the chances of the city seeing sporadic cases are rather large.”

When the new tests were implemented “very soon”, samples would be taken in wet markets that sold live poultry, said Dr Thomas Sit Hon-chung, assistant director of the Food and Environmental Hygiene Department.

Each test costs around HK$50 to HK$80 and it takes one day to get the result.

Health officials will also step up patrols at the 29 licensed poultry farms in the city and tighten supervision. If any samples tested positive, the government would halt market sales or suspend farm trading, Sit said.

The new move was announced after an interdepartmental meeting on the bird flu situation. Wong said the latest samples from live poultry markets on the mainland showed the contamination rate appeared to be rising.

Around 10 per cent of samples taken from Guangdong farms in January tested positive for the H7 virus, while 15.8 per cent tested positive in Jiangsu province, Wong said.

“It is a concern for the mainland as well as Hong Kong because of the proximity as well as high volume of traffic crossing the boarder,” Wong said. “It is important to detect as early as possible if there is human case.”