The WHO has raised its alert level from three to four, two steps short of declaring a full pandemic. Mexico earlier said it believed 149 people had now died from the swine flu, though only 20 cases are confirmed. The US, Canada, Spain and Britain have confirmed milder versions.
The WHO's decision to raise the alert level to four came after an emergency meeting of experts, brought forward by a day because of concerns over the outbreak. Level four means the virus is showing a sustained ability to pass from human to human, and is able to cause community-level outbreaks.
WHO PANDEMIC ALERT PHASES
Phase 1: No viruses circulating among animals causing infections in humans
Phase 2: Animal influenza virus causes infection in humans, and is considered potential pandemic threat
Phase 3: Influenza causes sporadic cases in people, but no significant human-to-human transmission
Phase 4: Verified human-to-human transmission able to cause community-level outbreaks. Significant increase in risk of a pandemic
Phase 5: Human-to-human transmission in at least two countries. Strong signal pandemic imminent
Phase 6: Virus spreads to another country in a different region. Global pandemic under way