The World Health Organization warned countries around the world Saturday to be on alert for any unusual flu outbreaks after a unique new swine flu virus was implicated in possibly dozens of human deaths in North America. WHO Director-General Margaret Chan said the outbreak in Mexico and the United States constituted a "public health emergency of international concern." The decision means countries around the world will be asked to step up reporting and surveillance of the disease, which she said had "pandemic potential" because it is an animal virus strain infecting people. But the agency cannot at this stage say "whether or not it will indeed cause a pandemic," she added. Chan made the decision to declare public health emergency of international concern after consulting with influenza experts from around the world. The emergency committee was called together Saturday for the first time since it was created in 2007. In theory, WHO could now recommend travel advisories, trade restrictions or border closures, none of which would be binding. So far it has refrained from doing so. The agency also held off raising its pandemic alert level, citing the need for more information. Earlier, Chan told reporters that "it would be prudent for health officials within countries to be alert to outbreaks of influenza-like illness or pneumonia, especially if these occur in months outside the usual peak influenza season." "Another important signal is excess cases of severe or fatal flu-like illness in groups other than young children and the elderly, who are usually at highest risk during normal seasonal flu," she said. Several Latin American and Asian countries have already started surveillance or screening at airports and other points of entry. At least 62 people have died from severe pneumonia caused by a flu-like illness in Mexico, WHO says. Some of those who died are confirmed to have a unique flu type that is a combination of bird, pig and human viruses. The virus is genetically identical to one found in California. U.S. authorities said eight people were infected with swine flu in California and Texas, and all recovered. So far, no other countries have reported suspicious cases, according to WHO. But the French government said suspected cases are likely to occur in the coming days because of global air travel. A French government crisis group began operating Saturday. The government has already closed the French school in Mexico City and provided French citizens there with detailed instructions on precautions. Chilean authorities ordered a sanitary alert that included airport screening of passengers arriving from Mexico. No cases of the disease have been reported so far in the country, Deputy Health Minister Jeanette Vega said, but those showing symptoms will be sent to a hospital for tests. In Peru, authorities will monitor travelers arriving from Mexico and the US and people with flu-like symptoms will be evaluated by health teams, Peru's Health Ministry said. Brazil will "intensify its health surveillance in all points of entry into the country," the Health Ministry's National Health Surveillance Agency said in a statement. Measures will also be put in place to inspect cargo and luggage, and to clean and disinfect aircraft and ships at ports of entry. Some Asian nations enforced checks Saturday on passengers from Mexico. Japan's biggest international airport stepped up health surveillance, while the Philippines said it may quarantine passengers with fevers who have been to Mexico. Health authorities in Thailand and Hong Kong said they were closely monitoring the situation. Asia has fresh memories of an outbreak of severe acute respiratory syndrome, or SARS, which hit countries across the region and severely crippled global air travel. Indonesia, China, Thailand, Vietnam and other countries have also seen a number of human deaths from H5N1 bird flu, the virus that researchers have until now fingered as the most likely cause of a future pandemic. The Dutch government's Institute for Public Health and Environment has advised any traveler who returned from Mexico since April 17 and develops a fever over 101.3 degrees Fahrenheit (38.5 Celsius) within four days of arriving in the Netherlands to stay at home. The Polish Foreign Ministry has issued a statement that recommends that Poles postpone any travel plans to regions where the outbreak has occurred until it is totally contained. The Stockholm-based European Center for Disease Prevention and Control said earlier Saturday it shared the concerns about the swine flu cases and stood ready to lend support in any way possible.