As the 2009 pandemic evolves, the data needed for risk assessment, both within affected countries and at the global level, are also changing.

At this point, further spread of the pandemic, within affected countries and to new countries, is considered inevitable.

This assumption is fully backed by experience. The 2009 influenza pandemic has spread internationally with unprecedented speed. In past pandemics, influenza viruses have needed more than six months to spread as widely as the new H1N1 virus has spread in less than six weeks. 

Go now to: WHO | Pandemic (H1N1) 2009 briefing note 3