WHO declares swine flu outbreak "public health emergency"

Medical team members wear masks as they walk in downtown Mexico City, capital of Mexico, April 25, 2009.  (Xinhua Photo)

The WHO's pandemic alert includes altogether six phases. "Phase3" means "no or very limited human-to-human transmission."

The emergency committee was established in compliance with the International Health Regulations (2005). It convened its first meeting on Saturday to assess the swine flu situation and advise the WHO chief on appropriate responses.

After reviewing available data on the current situation, committee members identified a number of gaps in knowledge about the clinical features, epidemiology, and virology of reported cases and the appropriate responses, the WHO statement said.

The committee also noted that answers to several specific questions were needed to facilitate its work.