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.
World health officials, whose warnings have helped brake the disease's global spread, kept a close eye on Europe for signs of a sustained rise between people there, which would mean the flu was officially a pandemic.
The Netherlands confirmed a second case of the virus, in a 53-year-old woman who had been in Mexico.
H1N1, which has killed a woman and a child in the United States but no one else outside Mexico, has reached 24 countries and infected more than 2,000 people, according to data from the World Health Organization and national authorities.
Sweden and Poland confirmed their first cases on Wednesday.
The new flu, a mixture of swine viruses and elements of human and bird flu, has taken the world to the brink of a pandemic and stoked trade and diplomatic tensions as China and some other nations quarantined Mexican citizens and products.
Mexican President Felipe Calderon accused these countries of ignorance. They included Haiti, the poorest nation in the Americas, which turned away a Mexican aid shipment of maize, wheat, beans and medicines, he said.
On Thursday, China began lifting a seven-day quarantine for passengers who had arrived on a flight from Mexico City which included a man who tested positive for H1N1, the Health Ministry said.
The dozens of Mexicans had been caught up in a wider drama about how far governments could go to stifle fears the virus could creep across their borders.
China's official Xinhua news agency also said 25 Canadian students had been released from quarantine in northeastern Changchun. None had shown flu symptoms.
The WHO now finds itself in a bind about how to respond to the spread of a virus whose effects have proved mainly mild.
The U.N. agency's guidelines state that as soon as the virus starts spreading freely in two regions of the world, its six-point pandemic alert should be raised to the top notch.
With infection numbers rising in Europe, public health experts are struggling to decide whether it is worth sounding the full alarm over H1N1, which is treatable with existing drugs and appears less severe than seasonal flu in most cases.
It is a judgment call, one WHO official said when asked about whether the global alert needs to hit its top rung.
WHO Director-General Margaret Chan raised it to level 5 -- signaling a pandemic was imminent -- last week after the flu strain that killed young adults in Mexico emerged in the United States and Canada and spread from schools to communities there.
Traffic again clogged Mexico's sprawling capital, home to 20 million people, and taco vendors worked the sidewalks again as Mexicans emerged from what was described as a forced vacation.
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. City officials said bars, restaurants, stadiums and cinemas will reopen on Thursday.
It still feels strange because there aren't many customers, said restaurant cook Rosa Avila.
U.S. health authorities remained on the alert with the Centers for Disease Control and Prevention (CDC) 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 because it has also killed some young and apparently healthy adults in Mexico. Influenza normally has a much higher death rate for the old, very young and frail.
Poland's first case was found in a 58-year-old woman, but her condition was not serious. Sweden's first case was in a person recently returned from the United States.
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.
PORK BANS CRITICISED
The flu has prompted some 20 nations to ban imports of pigs, pork and meat products from Mexico, the United States and Canada, which in protest have urged the world not to use the crisis 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.
But the WHO said on Wednesday meat from pigs infected with the new H1N1 virus should not be eaten by humans.