In spring, McDonald’s Japan usually serves up a seasonal special: a breakfast sandwich made of ginger, apples, sausage and an egg. Not this year. The fast-food chain is one of a growing number of companies in the country suspending sales of egg-related items.

Japan has culled about 15mn birds, as it deals with its worst-ever outbreak of bird flu. As a result, wholesale prices of eggs in February almost doubled. The shortages are widely felt. Convenience stores including 7-Eleven have suspended the sale of some egg-related products. Ingredient prices for food companies are rising across the board.

The biggest problem is with mayonnaise. Egg yolks are a key ingredient of this staple Japanese condiment. Manufacturers including the largest, Kewpie and Ajinomoto, will raise prices by up to 21 per cent from April. The cost of tartare sauce is also soaring.