Moon Hong-nam, a pastry chef in Seoul, needs at least 15,000 eggs a day to bake cakes, but after South Korea's worst outbreak of bird flu and a surge in the prices of eggs, he is considering changing his menu.

"We can ride it out through Christmas with what (supplies) we have secured," said Moon, who works at the LeSCARGOT bakery in the city. "But if (bird flu) continues until January, we will have to raise prices inevitably and make bakery items that do not need eggs."

About 20 million birds, nearly a quarter of South Korea's poultry stock, have been culled to control the outbreak. Most of the birds culled are egg-laying hens.