| MEXICO CITY
MEXICO CITY Mexicans got back into the swing of normal life on Wednesday after a five-day business shutdown due to the H1N1 flu virus, which spread in Europe with new infections in Poland and Sweden.
Mexico raised its confirmed death toll from the swine flu outbreak to 42 from 29, but the government says the worst is over and has eased curbs on commercial and public activity.
Nevertheless, the H1N1 virus, which has killed a woman and a child in the United States, advanced in Europe, with Sweden and Poland confirming their first cases. The flu has reached 24 countries, infecting over 2,000 people, according to data from the World Health Organization and national authorities.
The new flu, a mixture of swine viruses and elements of human and bird flu, has brought the world to the brink of a pandemic and has stoked trade and diplomatic tensions as some nations quarantined Mexican citizens and products.
Mexican President Felipe Calderon accused these countries, among them China, of "ignorance." They included Haiti, the poorest nation in the Americas, which turned away a Mexican aid shipment of maize, wheat, beans and medicines, Calderon said.
Traffic clogged Mexico's sprawling capital and taco vendors worked the sidewalks again as Mexicans resumed their normal lives after days cloistered at home.
U.S. health authorities remained on the alert with the Centers for Disease Control and Prevention reporting 642 confirmed cases of the H1N1 flu in 44 states.
The new virus appears to act like a seasonal flu but has confused doctors as it has also killed some young and apparently healthy adults in Mexico -- not the usual pattern for influenza, which normally has a much higher death rate for the old, very young and those with existing health problems.
U.S. CDC officials warned the American public not to become complacent over the apparent initial mildness of the outbreak.
"The risk of complacency, or a sense that we have weathered this, is a serious one," Stephen Redd, the CDC's director of Influenza Coordination, said in Atlanta.
RISK OF RESURGENCE
The U.S. confirmed cases showed a nearly 60 percent rise from Tuesday and Health and Human Services Secretary Kathleen Sebelius said more hospitalizations and deaths were likely.
For authorities worldwide, the question remained how far the virus would spread and how serious would it be. The WHO is at alert level 5. A level 6 alert would mean a full pandemic.
"What we are going to be looking very hard at over the months to come is what's happening in other parts of the world and really trying to understand whether we would be at risk for a resurgence in the fall," the CDC's Redd said.
Poland's first case was found in a 58-year-old woman, but her condition was not serious.
Sweden confirmed its first case in an individual who recently returned from the United States.
If the WHO detects a sustained spread within Europe -- as in North America -- it could officially declare a pandemic.
In Mexico City, home to 20 million people, security guards ran heat scanners over office workers to check they were free of fever, one of the flu's symptoms, as they returned to work.
"It was like a forced vacation. It still feels strange because there aren't many customers," said restaurant cook Rosa Avila.
Canadian researchers reported a second strain, of seasonal H3N2 influenza, may have mutated and may be complicating the outbreak picture in Mexico.
PORK BANS CRITICIZED
WHO experts will meet next week to consider whether drug makers should switch from seasonal to pandemic flu production in response to the new H1N1 strain.
U.S. regulators approved a new flu vaccine manufacturing plant to boost not only production of seasonal flu shots, but also possible vaccines to protect against H1N1.
The flu has prompted some 20 nations to ban imports of pigs, pork and meat products from Mexico, the United States and Canada. The three countries protested, urging the world "not to use the outbreak of the H1N1 human influenza as a reason to create unnecessary trade restrictions."
"H1N1 human influenza viruses are not spread by food," their agriculture ministers said in a joint statement.
However, the WHO said on Wednesday meat from pigs infected with the new H1N1 virus should not be eaten by humans.
Mexico fears the outbreak will knock up to half a percentage point off its growth this year. Mexican pork producers said they had lost $38 million in sales.
The Mexican government has angrily accused some countries, especially China, of displaying xenophobia and discrimination by restricting the free movement of Mexican citizens.
Mexicans stuck in forced quarantine in China arrived home in a government-chartered plane.
(Reporting by Louise Egan, Dan Trotta, Miguel Angel Gutierrez in Mexico, Matt Bigg in Atlanta, Maggie Fox, Susan Heavey, Lisa Richwine in Washington, Laura MacInnis, Jonathan Lynn in Geneva, Tan Ee Lyn in Hong Kong; Writing by Pascal Fletcher; Editing by Eric Beech)