China yesterday urged local governments to be on full alert, warning that the country will be more vulnerable to swine flu during the busy May holiday travel period.

"Travel agencies, hotels, scenic spots, and tour buses and ferries should strengthen sanitation and take precautions to deal with a possible epidemic," the National Tourism Administration (NTA) cautioned on its website.

Mainland tourism departments must be on duty 24 hours a day and maintain close contact with Hong Kong, Macao and Taiwan - three major sources of overseas travelers, the NTA said.

The move came one day after China restricted travel to Mexico, the country at the center of the outbreak.

Zhang Shuo, manager of the marketing department at China International Travel Services, said yesterday the agency has stopped organizing tours to Mexico. But foreign tourists continue to enter China, Zhang said.

Chinese tourists returning from flu-hit areas and foreign tourists arriving in China from impacted areas have not caused any problems so far, the NTA said yesterday.

The Shanghai tourism bureau said three Shanghai tourists are still in Mexico and 437 are in the United States. They have been urged to wear masks and contact Chinese embassies if they develop flu symptoms.

Gu Xiaoyuan, vice-director of the Beijing tourism bureau, said yesterday: "There will be two tour groups from Mexico to Beijing in the coming month, members of which will be examined."

Swine flu is suspected in the deaths of more than 150 people in Mexico and the US. It has spread to New Zealand, Israel, Canada, the UK and Spain.

Chinese tour agencies became increasingly concerned after Asian countries including Thailand and South Korea reported suspected cases.

"Some tourists cancelled their plans to the United States and Canada," Zhang said.

Officials from Pudong International Airport said passengers from flu-hit regions will be screened.

Anyone whose temperature exceeds 37.5 C will be sent to the Shanghai Public Health Center for further checks.

Questions:

1. What country is at the center of the swine flu outbreak?

2. What areas are the three major sources of overseas travelers?

3. Passengers at Pudong International Airport will be sent to the Shanghai Public Health Center for further checks if they have what?

Answers:

1. Mexico.

2. Hong Kong, Macao and Taiwan.

3. A temperature exceeding 37.5 C.