SHANGHAI: The city is geared up to ensure health care services for the estimated 70 million visitors to the upcoming Shanghai World Expo, though a new outbreak of the H1N1 flu could be a major threat.

Shen Xiaoming, vice mayor of Shanghai, warned yesterday that H1N1 could still be a health challenge at the cultural gala, though flu cases caused by the virus in Shanghai accounted for only 20 percent of all flu cases at the beginning of this year. This is down from 90 percent in the flu's peak period in the second half of 2009.

"A new type of flu always needs two to three years to scale down. Only one year has passed since the first case was reported in Shanghai," Shen said.