The heads of the United Nations and the World Health Organization say there are no imminent plans to raise its pandemic alert to its highest level. In New York on Monday, UN Secretary-General Ban Ki-moon said WHO "has no plan to raise the alert level to 6 at this moment." WHO chief Margaret Chan also told the UN General Assembly by video-link from Geneva that "we are not there yet." Level 6 - the highest - would mean that a global outbreak of swine flu is under way. WHO raised the level to 5 last week. Chan said there were now more than confirmed cases of swine flu in 20 countries, and there is "no indication" the situation is similar to the flu outbreak in 1918. Ban and Chan say there was no justification now for banning imports based on swine flu. Meanwhile, Mexico chartered a plane to China to bring home 70 of its citizens who were seized at the airport and quarantined, declaring that the swine flu epidemic was no reason for "repressive and discriminatory measures." Mexican officials also declared the epidemic to be waning, but medical experts worldwide said it was to early to make that call. While Mexico began its first tentative steps toward normalcy, weighing whether to reopen businesses and schools, the virus spread to Colombia in the first confirmed case in South America, where flu season is about to begin. A New York City school that had closed after dozens of students were infected with the virus reopened Monday. More cases were confirmed in North America and Europe - including Portugal's first - with the total number sickened worldwide rising to more than a 1,000 people, according to health and government officials. But with the scope of the disease unknown, several countries have taken urgent measures against arriving Mexicans or those who have recently traveled to Mexico. In China, more than 70 Mexican travelers were quarantined in hospitals and hotels, and Mexicans on arriving flights were taken into isolation, said Mexico's ambassador, Jorge Guajardo. Even the Mexican consul in Guangzhou was briefly held after returning from a vacation in Cambodia. And in Hong Kong, 350 people remained isolated Monday in a hotel after a Mexican traveler there was determined to have swine flu. One guest, Briton Mark Moore, complained that he had not shown symptoms and urged the government to lift the quarantine. "The government is trying to show the world they are strong in organizing this," the 37-year-old Singapore-based company director said in a phone interview. "I need to be in Singapore now. I have loads of things to do." Mexican President Felipe Calderon complained of the backlash against Mexicans abroad. "I think it's unfair that because we have been honest and transparent with the world some countries and places are taking repressive and discriminatory measures because of ignorance and disinformation," Calderon said. "There are always people who are seizing on this pretext to assault Mexicans, even just verbally." The president did not single out any country. But the Foreign Relations Department said afterward that Mexico was sending a chartered jet Monday to bring back any citizens who wanted to leave China.