(AP) -- Traffic is picking up again, cafes are reopening and cleanup crews are getting universities ready to resume classes. Mexico City has some of its customary bustle back, and the president promises life is returning to normal after a five-day shutdown to contain the spread of swine flu.
Mexico still called off Cinco de Mayo celebrations Tuesday, including the biggest one of all - a re-enactment of the May 5, 1862, victory over French troops in the central state of Puebla. And health experts warned that Mexico and the rest of the world needed to remain on guard against the virus.
Saying the outbreak is waning in Mexico, the epicenter of an illness that has sickened hundreds around the world, President Felipe Calderon announced it was nearly time to reopen businesses. Universities and high schools will open their doors Thursday, and younger schoolchildren are to report back to school May 11.
"The school schedule will resume with the guarantee that our educational institutions are in adequate hygienic condition," Calderon said. He urged parents to join educators in a "collective" cleansing and inspection of schools nationwide.
"This is about going back to normalcy, but with everyone taking better care," Calderon said.
Already more vehicles prowled the streets of the capital Monday than over the weekend, and fewer people wore surgical masks. Some cafes even reopened ahead of time.
Health Secretary Jose Cordova said infections were trending downward after Mexico's 27 deaths, including a Mexican toddler who died in Texas. He said those infected appeared to pass the virus on to an average of 1.4 other people, near the normal flu rate of around 1.3.
Cordova said soccer stadiums and concert halls could reopen - but only if fans were kept 2 meters, about 6 1/2 feet, apart.
However, world health officials stressed that the global spread of swine flu was still in its early stages and a pandemic could be declared in the days to come. Experts inside Mexico's swine flu crisis center warned that the virus remained active throughout Mexico and could bounce back once millions return to work and school.
"It's clear that it's just about everywhere in Mexico," Marc-Alain Widdowson, a medical epidemiologist from the U.S. Centers for Disease Control and Prevention, told The Associated Press.
Scientists said the virus is spreading in the U.S. and that chances of severe cases could rise there as well, even as a New York City school reopened after the swine flu hit following a spring break trip by some students to Mexico.
"We are by no means out of the woods," said Dr. Richard Besser, acting director of the CDC.
As of Monday, Mexico had 802 confirmed cases, and U.S. cases grew to at least 380 in 36 states. Globally, the virus had infected more than 1,445 people in 20 countries, according to the World Health Organization and other health bodies. South Korea reported its second confirmed case and Italy reported its fifth Tuesday. Experts said the known cases were almost certainly only a fraction of the real total.
The latest figures from Mexico suggest the virus may be less lethal and infectious than originally feared. Only 38 percent of suspected cases have turned out to be swine flu, and no new deaths have been reported since April 29. But Cordova acknowledged that about 100 early deaths in which swine flu was suspected may never be confirmed because mucous or tissue samples were not collected.
WHO was studying whether to raise the pandemic alert to 6, its highest level, which would mean a global outbreak had begun. WHO uses the term pandemic to refer only to geographic spread and not to the severity of an illness. The two most recent pandemics - in 1957 and 1968 - were relatively mild.
"We do not know how long we will have until we move to Phase 6," WHO Director-General Margaret Chan said. "We are not there yet. The criteria will be met when we see in another region outside North America, showing very clear evidence of community-level transmission."
The Southern Hemisphere is particularly at risk. While Africa still hasn't reported any swine flu infections and New Zealand is the only country south of the equator with confirmed cases, winter is only weeks away. Experts worry that typical winter flus could combine with swine flu, creating a new strain that is more contagious or dangerous.
"You have this risk of an additional virus that could essentially cause two outbreaks at once," Dr. Jon Andrus said at the Pan American Health Organization's headquarters in Washington.
Still, the U.N. health agency urged governments to avoid unproven actions to contain the disease, including group quarantines of travelers from Mexico and bans on pork imports.
China, Argentina and Cuba are among the nations banning regular flights to and from Mexico, marooning passengers at both ends. Mexico and China both sent chartered flights to each other's countries to collect their citizens, with a chartered Mexican plane landing in Shanghai early Tuesday. Argentina also chartered a flight to bring Argentines home.
In a televised message to the country late Monday, Calderon had harsh words for countries that he said are treating Mexicans unfairly. "Stop taking actions that only hurt Mexico and don't contribute to avoid the transmission of the disease."
Chinese authorities quarantined Mexicans and other passengers who came in close contact with them, even those who didn't show symptoms.
The American Embassy in Beijing said Tuesday that four U.S. citizens were quarantined in China. Embassy spokeswoman Susan Stevenson said two of the Americans were in Beijing and the other pair were in the southern province of Guangdong. She said two of them were released.
In Tokyo, 37 passengers and two flight attendants on a flight from Los Angeles were detained in a hotel after Japanese officials suspected one traveler of having swine flu. They were released about 10 hours later when the passenger, a Japanese woman coming back from Las Vegas, tested negative for swine flu, American Airlines spokesman Tim Smith said.
About 200 passengers who flew from the United Kingdom to Brunei were under quarantine in a Brunei hospital over swine flu fears Tuesday after three of them showed fever symptoms, an official said Tuesday.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Discovery of a new therapeutic target to fight against Legionella