The global chicken chain has been forced to keep almost all its outlets in Vietnam closed after the illness killed six people in the country.

Now, with customers shying away from its normal fare, it is switching to an all-fish menu.

The only way to return to the usual menu, KFC said, might be to start importing frozen chickens from the US.

Popularity

KFC, together with a crop of lookalike competitors, has been a success in Asia, where poultry has familiarity on its side while burgers do not.

Out of 12,500 restaurants worldwide, more than 3,000 are in Asia - a third in Japan, 900 in China and Hong Kong, and another 300 or so in each of Thailand and Malaysia.

KFC's nine outlets in Vietnam were closed anyway for the Chinese New Year earlier this month, but are now likely to stay shut until 31 January.

Its restaurants elsewhere have yet to be similarly affected.

Precaution

The move could be as much a precautionary public relations move as a health protection measure.

The World Health Organisation says so far bird flu has been passed on by bird droppings, not by well-cooked meat.

That idea seemed to have struck home with some customers.

"I'd never even thought about it, but if you'd asked me before I came in, I definitely would not have done," one expatriate customer in Bangkok told Reuters.