The World Health Organisation (WHO) has given a warning that the flu, which has killed 47 people in Asia, could mutate into a form that spreads quickly between humans and trigger a global pandemic.
Britain has stockpiled more than 14m courses of the antiviral drug Tamiflu at a cost of £200m, enough to treat a quarter of the population.
The bird flu has a mortality rate of 60-80% and the government says 50,000 people could die if it takes hold here — four times the number who die each year from influenza.
So far there have been five suspected instances of bird flu among poultry in Britain, but no human cases. Health experts have called for a ban on imports of poultry feathers from Asia.