The death toll from a swine flu outbreak in Mexico has reached 149 as health chiefs warn of a looming pandemic. The World Health Organisation has lifted its pandemic alert from phase 3 to phase 4, indicating the risk of a deadly global outbreak. No one has died from the swine flu outside Mexico but it has infected more than 50 people in the US, six in Canada, two in Scotland, 11 in New Zealand, one in Israel and two in Spain. Possible cases are being tested as far apart as Norway and South Korea. Worried Mexicans are wearing masks while airlines check passengers for flu symptoms and governments warn against non-essential travel to Mexico. Mexico City Mayor Marcelo Ebrard said: "We will defeat this threat." Governments around the world are moving to prevent a possible flu pandemic. The European Commission has called an urgent meeting of Health Ministers in Brussels. In Asia, health officials say they have enough anti-flu drugs to deal with an outbreak. Increased surveillance at airports and ports includes the use of thermal cameras and sensors to single out people with a fever. A global outbreak could cost the world economy $3 trillion (£2tn) according to calculations by the World Bank in 2008. Shares in Asia and Europe have fallen, although pharmaceutical companies which make vaccines and drugs have seen their stock rise.