Joe Greco, who’s been churning out cookies and cakes for 27 years, usually uses about 600 pounds of liquid eggs a week at his bakery near Chicago. Now, his freezer has seven times that amount because Greco worries that record prices are about to go even higher.

The cost of breaker eggs — those cracked and sold in liquid form for use by wholesale bakers and restaurants such as McDonald’s Corp. — have more than doubled in the past three weeks. The culprit behind the surge: the worst-ever American outbreak of the bird flu virus.

More than 33.5 million chickens, turkeys and other birds have been affected. Iowa, the top U.S. egg producer, was hardest hit, losing 40 percent of its laying hens. The disease prompted the government to forecast the first annual drop in egg production since 2008. Greco is concerned his 4,200-pound (1,900-kilogram) stash of liquid eggs won’t protect him from higher costs, and that he’ll have to start buying eggs still in shells to crack by hand.

“As soon as I heard about the bird flu, I knew this was going to happen,” said Greco, 47, who owns Palermo Bakery in Norridge, Illinois, near Chicago’s O’Hare Airport. He’s been racing to buy extra supplies over the past month and saw prices for the pails of liquid eggs he buys jump 28 percent last week. “After the Fourth of July, there might be another nightmare, so I’m still shopping around to see if there are better prices.”

Highly pathogenic avian influenza spread rapidly through parts of the Midwest in the past two months, and Iowa lost about 23 million hens. Post Holdings Inc. has warned that bird flu will hurt fiscal 2015 earnings at its food-service unit, while countries in the Middle East and Asia have placed restrictions on shipments of U.S. poultry.

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