H5 virus which is responsible for avian flu, a disease that has forced a mass slaughter of poultry in many countries and could, if it mutates, cause a deadly epidemic among humans.

ECONOMIST: The World Health Organisation

Identifying human cases and isolating them quickly is important because the shortest route to a version of the disease that is dangerous to the whole of humanity rather than just vets and poultry farmers is simultaneous infection with both bird influenza and the human variety, and the exchange of genes between the two.

ECONOMIST: Bird flu and public health

The countries represented at the summit pledged a co-ordinated fight against the disease and issued a declaration that mass culling of infected poultry flocks was the best way to control its spread.

ECONOMIST: Averting a global plague | The

In some places, at least, ruthless monitoring of poultry flocks has reduced both the avian disease and the (already rare) cases of people becoming infected.

ECONOMIST: Bird flu and public health

Avian flu viruses can sometimes spread to domestic poultry and cause large-scale outbreaks of serious disease.

FORBES: Bird Flu Claims More Lives In Shanghai

Out of 218 confirmed human cases almost all those infected have caught the disease from poultry.

ECONOMIST: Down with the flu | The

Although the disease is currently a threat mainly to poultry, many are worried about the supply of anti-viral drugs and vaccines for a human pandemic.

ECONOMIST: Calls for more money as the threat looms ever larger | The