BIRD FLU OUTBREAKS IN 2005 (H5N1 STRAIN) The H5N1 strain remained largely in South-East Asia until this summer, when Russia and Kazakhstan both reported outbreaks Scientists fear it may be carried by migrating birds to Europe and Africa but say it is hard to prove a direct link with bird migration UK case discovered in quarantine, so disease-free status unaffected View the spread of bird flu on an interactive map

Countries around the world are bracing themselves to deal with the spread of avian flu, which has begun to break away from its original "hotspot" of South East Asia.

Outbreaks of the latest H5N1 strain among birds were first spotted in Vietnam and Thailand in 2003. It spread to several other countries in the region, and has now established a toehold in eastern Europe.

The World Health Organization puts the number of human deaths at more than 70 out of a total of more than 130 human cases.

The disease generally still does not transmit easily to humans, but its emergence in Turkey, Croatia and Romania in the autumn - has raised fears of a pandemic, prompting the WHO to urge heightened surveillance and vigilance.

It warns: "Each additional human case increases opportunities for the virus to improve its transmissibility, through either adaptive mutation or re-assortment.

"The emergence of an H5N1 strain that is readily transmitted among humans would mark the start of a pandemic."