"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.

CNN: WHO raises pandemic alert to second-highest level

The WHO's "Phases of Pandemic Alert, " which has been in existence for five years, characterizes phase 5 as a human-to-human spread of the virus into at least two countries in one WHO region, signaling that a pandemic is imminent.

CNN: WHO raises pandemic alert to second-highest level