The Chinese mainland reported its first suspected case of A(H1N1) yesterday and health authorities quarantined seven people who flew in from North America, raising fears of a possible outbreak.

A 30-year-old man surnamed Bao has tested positive for the H1N1 virus in Sichuan province but the Ministry of Health (MOH) has not confirmed the case. That may be because MOH is conducting further tests, an expert said.

Bao flew from St Louis in the US to Tokyo on Friday. He landed in Beijing from Tokyo on flight number NW029 on Saturday, and took the U8882 flight to Chengdu, capital of Sichuan province, the same day.

He showed flu symptoms after reaching Chengdu, went to the Sichuan Provincial People's Hospital for a check-up, and tested "positive" for the H1N1 virus after two rounds of tests.

The MOH has launched a campaign to locate 144 passengers who flew with Bao to Chengdu.

Guan Yi, a microbiology professor in the University of Hong Kong, told China Daily: "The MOH may need more time to confirm it, but it looks likely to be the first confirmed case on the mainland."

Four of the seven people, including an American, who flew in from North America have been quarantined in Shanghai. The other three are quarantined in Beijing, and Anhui and Jiangsu provinces.

The flight, NW025, which the seven took from Ontario in Canada to Tokyo also carried four Japanese passengers - a teacher and three students - who later tested positive to the H1N1 virus.

Seventeen passengers on the NW025 flight changed for Taiwan in Tokyo, and one flew to Hong Kong. The 16 who visited Taiwan have tested negative for the flu virus, and the two, including one who flew via Taiwan, to Hong Kong have been quarantined.

"We will keep abreast of the developments, and strengthen our countermeasures with the help of other countries and the World Health Organization (WHO) ," the MOH said.

Twenty-nine countries had reported 4,379 cases by 07:30 GMT yesterday, the WHO said. The figure was 2,500 on Friday.

The US has the maximum number of confirmed cases, 2,254, followed by Mexico (1,626) and Canada (280), the WHO said. But most of the flu-related deaths have occurred in Mexico (45). Two persons have died in the US, and one each in Canada and Costa Rica.

Experts, however, urged people on the mainland to stay calm despite the suspected case in Sichuan and a jump in the number confirmed cases worldwide over the weekend. "I'm not surprised at the sharp increase (it) is quite normal because the flu epidemic is developing gradually," Guan said.

"People should not panic because an epidemic is unlikely to break out on the mainland," said Yin Kaisheng, an expert with the Chinese Society of Respiratory Diseases. The experience gained by the authorities in fighting the SARS epidemic will help them check the spread of the H1N1 flu, he said.

"The death rate in H1N1 cases is 1-2 percent, which is very low compared to SARS and bird flu," Nanjing-based Xinhua Daily quoted Zhong Nanshan, a respiratory scientist, as having said. Zhong is respected for his work in the fight against SARS.