What changes are needed for the H5N1 virus to affect humans and become pandemic?
The virus can become transmissible among humans by either a “reassortment” event or by a more gradual process of adaptive mutation. In “reassortment” genetic material is exchanged between human and avian viruses when there is co-infection in a human or pig. This results in a new potent strain that is fully transmissible to humans. The process of adaptive mutation is a more gradual process by which the virus becomes more efficient at binding to human cells. A pandemic can start when three conditions have been met: a new virus subtype emerges; it infects humans; and it spreads easily and is sustained among humans. The first two conditions have been met in that a new subtype has emerged and humans have been infected through contact with infected birds.
