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International

Six distinct phases have been defined by the World Health Organization to help global preparedness planning:

Inter-pandemic Period – new virus in animals, no human cases

Phase 1  Low risk of human cases
Phase 2  Higher risk of human cases

Pandemic Alert Period

Phase 3  No, or very limited, human-to-human transmission
Phase 4  Evidence of increased human-to-human transmission
Phase 5  Evidence of significant human-to-human transmission

Pandemic Period

Phase 6  Efficient and sustained human-to-human transmission

We are currently in Phase 3 as a virus new to humans is causing infections, but does not spread easily from one person to another.

Experts are concerned because the H5N1 virus currently circulating among birds in Africa, Asia and Europe has demonstrated the ability to cross the species barrier to cause disease and death in humans.

The World Health Organization (WHO) alert level remains at Phase 3 and a particular risk of pandemic emergence arises through adaption of the virus or recombination with circulating (human) viruses.

Although there have been no major changes in the behaviour of H5N1 viruses in humans or animals since they emerged a decade ago, it is possible that they could change suddenly. This could lead to more efficient transmission among humans.

The World Health Organization (WHO) continues to monitor the situation carefully.