On April 29, 2009, the World Health Organization (WHO) raised its influenza (flu) pandemic alert level to Phase 5, one level below declaring that a global influenza pandemic was underway. According to WHO, 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. The WHO has increased the pandemic flu alert level in response to the spread of a new strain of influenza A subtype H1N1 virus.