The Conversation On November 13, Spain’s Ministry of Agriculture, Fisheries and Food imposed the confinement of all free-range poultry farms to curb the spread of avian influenza – more commonly known as “bird flu” – caused by the H5N1 virus. This drastic, though not unprecedented, measure was justified by climbing numbers of outbreaks in Europe, as well as the heightened risk posed by the southward migration of wild birds in Europe.
This type of news understandably causes alarm among the general public, but has the risk of the H5N1 virus triggering a pandemic among humans actually increased? And why is it causing increasing devastation not only among birds, but also among many species of mammals?
Masters of variability
Flu viruses come in many forms. There are four strains (A, B, C, and D), each with many different sub-types.
Type A viruses are the most significant for human and animal health, and they are all descended from avian viruses. The flu A virus has two essential proteins in its envelope: haemagglutinin (H) and neuraminidase (N). There are 18 types of H and 11 types of N, which can be found in any combination: H1N1, H1N2, and so on up to H18N11.