What was once a cheap source of protein has become a luxury breakfast food. Egg prices have soared over the past year, as the worst avian flu outbreak in U.S. history has infected more than 57 million chickens.

The consumer price index reports an increase of 59% year-over-year and 11.1% from November to December. The average price of a dozen eggs went from $1.50 in January 2022 to more than $5 this month.

Phillip Braun is a professor of finance at Northwestern University’s Kellogg School of Management. He said inflation has affected feed and other aspects of egg production, but it’s the flu that’s driving up prices.

“In December, one big issue with the price increase was increased demand because of the holidays," Braun said. "The holidays are past, so the expectation is there will be lower demand for eggs going into the future. And those that still want to consume eggs — it’s definitely going to put a pinch into their household budgets.”

Cliff McConville is the owner of All Grass Farms. His farm is part of an association that keeps birds outdoors, raised by pasture. McConville said keeping thousands of birds confined makes the contagion of avian flu even worse and that it takes weeks to raise egg-laying hens. For that reason, he said, the egg shortage is likely going to last longer than expected.

“If avian influenza wipes out all the laying hens in a chicken house, say they were in mid-production ... .There’s not a ready supply of replacement pullets," McConville said. "... It takes about 20 weeks to raise a chicken old enough to start laying eggs.”