The recent appearance of the H5N1 bird flu in pigs does raise viral reassortment concerns. Here's what we know about this highly pathogenic avian influenza virus so far.

A recent study shows a mild increase in the H4N1 strain of bird flu transmissibility through air compared to older variants.

A World Health Organization official on Thursday called for stronger surveillance in animals for evidence of infection with H5N1 bird flu in order to curb its spread. The official also urged stronger efforts to reduce the risk of transmission of the virus to new species of animals and to humans.

The developing avian influenza panzootic and the growing possibility of a pandemic bring to the fore the existential questions for humanity of climate change and the destruction of public health, both of which must be stopped in order to control the growing threats.