Why the concern about the current outbreaks?
Most of the outbreaks recently reported in Asia have been caused by the highly pathogenic H5N1 strain, which mutates rapidly and has a documented propensity to acquire genes from viruses infecting other animal species. Its ability to cause severe disease and death in humans has now been documented. The greater concern is the possibility that the present situation could give rise to another influenza pandemic in humans. Avian and human influenza viruses can exchange genes when a person is simultaneously infected with viruses from both species. This process of gene swapping inside the human body can give rise to a completely new subtype of the influenza virus to which few, if any, humans would have natural immunity. If the new virus contains sufficient human genes, transmission directly from one person to another (instead of from birds to humans only) can occur. When this happens, the conditions for the start of a new influenza pandemic will have been met. Most alarming would be a situat
