The second shipment of Chinese anti-flu aid arrived in Mexico early on Monday, when President Felipe Calderon ordered to reopen schools in the coming days.

Also on Monday, Mexico City began a new system of five alerts and placed the current situation in the middle of the scale. Officials also reported a third day without any death linked to the flu, which has now spread to 21 nations.

"So that parents and the education community can... feel secure that children and young people are returning to classes in a secure and healthy environment, I have instructed the public education minister that the return to classes be gradual," Calderon told media.

Institutions of higher learning will reopen on Thursday, while nurseries and primary schools will resume next Monday. The nationwide school closure was probably the most drastic measure implemented to fight the spread of the disease, affecting around a third of the population directly and with knock-on effects on relatives who were forced to stay at home with children.

Calderon also urged citizens to continue with measures designed to fight the disease, and asked parents to cooperate in organizing security and health measures at education institutions attended by their children.

"The coming days and weeks will be crucial so that we will not lower our defenses nor neglect all that has been achieved in these days of enormous social, personal, family and financial efforts by millions and millions of Mexicans," Calderon said.

China's aid shipment, some 70 tons of medical and hygiene equipment including face masks, latex gloves and thermometers, arrived in Mexico City International Airport at 7:04 AM local time (1300 GMT) aboard a Southern Airlines flight.

China's ambassador to Mexico Yin Hengmin received the aid at the airport's presidential hangar, together with Rogelio Granguillhome, head of the international cooperation and economic relations department under the Mexican foreign ministry.

Last Wednesday, China pledged US$5 million in aid for Mexico: 4 million in material and 1 million in cash. Monday's flight was the second delivery, after Friday night shipment formally received by the president.

Also on Monday, Mexico City, worst hit by new A/H1N1 flu strain,reported no new death in patients suffering flu-like symptoms, and a net fall in patients with flu in hospitals, to 76 from 84, as 20 people recovered from the disease, and only 12 new patients were hospitalized.

The city also unveiled a new five-stage epidemic alert system and said that current circumstances correspond to an orange alert, in the middle of the scale, and lifted the ban on gatherings.

"The alert system is going to be permanent... because this virus is going to be present in the coming weeks and because it can mutate so we have to be alert," said Mexico City's mayor Marcelo Ebrard Casaubon.

A green alert represents a normal situation, although city authorities must have minimum levels of equipment ready. The other alerts are yellow, orange, red and red-plus, with measures ranging from face masks for only workers that deal with a lot of people, at yellow alert; to the complete closure of the city, with only emergency services allowed on the streets, at red plus alert.

City officials also reported that health centers had received more than 2,800 people showing certain signs of the A/H1N1 flu, which include high fever, breathing difficulties, headaches and muscular pain.

Meanwhile, tourism officials in Baja California Sur, a state which does not have a single confirmed case, on Monday reported a sharp drop in tourist traffic scared off by news of the possible outbreak.

The resort has suffered cancellations that emptied 3,200 hotel rooms, Miroslav Bautista, director of tourism in the town of Los Cabos told media. Bautista said a total of 19 cruise ships had cancelled calls at the port of Cabo San Lucas, which means a decrease of arrivals by 40,000 people.