What does pandemic alert phase 5 mean?

According to WHO definitions of phases - the virus has caused sustained community level outbreaks in at least two countries in one WHO region. At phase 5 a pandemic is considered imminent.

What is sustained human to human transmission?

This occurs when three generations are involved - i.e. the virus has passed from person A to person B and then to person C.

What is the difference between a probable case and a confirmed case?

A probable case is one that shows the symptoms of influenza such as cough, fever, headache, chills and fatigue and either tests positive for type A influenza or is considered linked to another probable or confirmed case.

A confirmed case is one which tests positive in a laboratory for the influenza A(H1N1) virus.

At what point does WHO consider a pandemic to have started?

Phase 6, as defined by the WHO pandemic preparedness guidelines. However, during both phase 5 and phase 6, national and local actions to respond to the outbreak shift from preparedness to response at a global level. The goal of recommended actions during these phases is to reduce the impact of the pandemic on society.

(WHO May 3, 2009)