From the WHO at :
http://www.who.int/mediacentre/news/statements/2009/h1n1_20090429/en/index.html
"Statement by WHO Director-General, Dr Margaret Chan
29 April 2009
Swine influenza
Ladies and gentlemen,
Based on assessment of all available information, and following several expert consultations, I have decided to raise the current level of influenza pandemic alert from phase 4 to phase 5.
Influenza pandemics must be taken seriously precisely because of their capacity to spread rapidly to every country in the world. "
Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.