The story

The World Health Organization on Wednesday raised its pandemic alert to 5, its second-highest level, warning of widespread human infection from the swine flu outbreak that originated in Mexico.

Dr. Margaret Chan, the U.N. agency's director-general, said the decision to raise the alert on the 6-point scale indicated that all countries should "immediately" activate pandemic preparedness plans.

"This change to a higher phase of alert is a signal to governments, to ministries of health and other ministries, to the pharm industry and the business community that certain actions now should be taken with increased urgency and at an accelerated pace," Chan said. Read full article »

CNN's Dr. Sanjay Gupta and Barbara Starr contributed to this report.

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