World health officials tried to quell growing fears over swine flu, as governments braced for a global pandemic and the United States set up a lab in Mexico to help diagnose and test cases.
A day after upping its pandemic alert level, the World Health Organisation (WHO) said there was no evidence to suggest it should be raised to the maximum level of six.
Mexico raised the number of deaths from the disease to 12 and said it had 260 confirmed cases of swine flu. A Mexican toddler also died during a visit to Texas.
But amid questions over why Mexico has been hit so hard compared to other countries, European ministers rejected a French proposal for an EU-wide ban on travel to the tourist hotspot as excessive.
"We have to be careful, we have to exercise vigilance, we should not panic, we have to be prepared," EU Health Commissioner Androulla Vassiliou told an emergency meeting of health ministers in Luxembourg.
She warned that an international flu pandemic was "likely" although it would not necessarily cause widespread deaths.
"It is very likely that we will reach a pandemic, but this does not mean that it will be deadly," she told journalists.
Czech Health Minister Daniela Filipiova, who chaired the meeting, said the fact that there might be a pandemic only meant that "it may happen that an unusual amount of people may be ill."
US health officials meanwhile confirmed there were 118 cases of the H1N1 virus spread across 15 states, with the Centers for Disease Control and Prevention (CDC) giving assurances they would all receive ample supplies of anti-viral drugs.
Health and Human Services Secretary Kathleen Sebelius also announced the purchase of an additional 13 million antiviral treatments, as well as plans to send 400,000 of the treatments to Mexico.
The 251-million-dollar purchase replaces 11 million treatment courses the government has already offered to US states and buys an additional two million courses.
The White House confirmed an official who had been among President Barack Obama's delegation on a trip to Mexico earlier this month appeared to have contracted swine flu, and had likely infected three members of his family.
But the man, who dined with the president in Mexico City, was always more than six feet (two meters) away from the US leader, outside the infection zone.
A World Bank employee who traveled to Mexico was also diagnosed, the Washington-based bank said, adding some 80 fellow employees have been asked to work from home.
The United States has recorded the highest number of cases of swine flu outside Mexico, and has now set up a laboratory in Mexico to let scientists quickly diagnose cases of the H1N1 flu virus in the country.
Officials are trying to determine why so far all the deaths except one have occurred in Mexico, and why most victims elsewhere have only suffered mild symptoms.
Japan meanwhile reported its first suspected case of swine flu, a 17-year-old high school student who returned last weekend from Canada. And Britain, the Netherlands, and Switzerland all confirmed fresh cases of the virus. Some 13 countries outside of Mexico have now been affected.
However the sole case of swine flu identified in Peru was actually a misdiagnosis, the country's health minister admitted.
Canada also confirmed nine new cases of swine flu, raising its total number to 28, the third highest after Mexico and the United States.
In a televised address, Mexican President Felipe Calderon urged people to stay home during a five-day holiday weekend that starts Friday, and the country's traditional May 1 rallies have been canceled.
Mexico has shut down public venues and even bars in the capital, while major tour operators have halted trips to the country.
Mexico also said it would lodge a formal challenge in the World Trade Organization demanding countries banning its pork products explain the reasons for their decisions.
The query to be sent to the WTO will ask China, Russia and other countries for "an explanation for the restrictions adopted, including their scientific basis," the economy ministry said in a statement.
Health experts say the H1N1 virus cannot be transmitted by eating pork despite its original name of "swine flu."
Swine flu is believed to be a new strain that combines bird, swine and common human influenza. The WHO's phase five alert status signals widespread transmission from person to person and that a pandemic is imminent.
The UN organization meanwhile said it would begin referring to the swine flu virus as "influenza A (H1N1).
Pig farmers in many countries have been hit hard and are pressing governments to change the name of the virus.