The rising cost of eggs in the U.S. is denting household budgets. Americans in recent years have increased the number of eggs they consume while reducing their intake of beef and venison, according to  from the U.S. Department of Agriculture. 

Egg consumption has grown in part because more families are eating them as their main protein substitute, Los Angeles Times reporter Sonja Sharp told CBS News. "Each of us eats about as many eggs as one hen can lay a year," she said. 

As demand for eggs has risen, production in the U.S. has slumped because of the ongoing bird, or "avian," flu epidemic. Nearly 58 million birds have been infected with avian flu as of January 6, the USDA , making it the deadliest outbreak in U.S. history. Infected birds must be slaughtered, causing egg supplies to fall and prices to surge.

Egg prices in December rose 60% from a year earlier, according to Consumer Price Index released Thursday. Across U.S cities, the average price for a dozen large grade A eggs was $4.25 last month, according to  from the Federal Reserve Bank of St. Louis. 

In some states, it can even be hard to find eggs on the shelves. But egg supplies overall are holding up because the total flock of egg-laying hens is only down about 5% from from its normal size of around 320 million hens. Farmers have been working to replace their flocks as soon as they can after an outbreak.

Sharp said prices will likely not fall again until after new chickens are born without the infection and grow to egg-laying age. More than 300 flocks of farm-raised poultry have been hit by the outbreak as of last Friday, according to USDA . 

In New York, grocery store owner Jose Filipe said that soaring egg costs have caused many customers to change their spending habits.

"I've seen customers gravitate from buying organic eggs now to more conventional eggs, and specifically now, the half dozen. Prices have quadrupled in about six or seven months," he recently told CBS New York's Jenna DeAngelis.

What is avian flu?

Bird flu is carried by free-flying waterfowl, such as ducks, geese and shorebirds, and infects chickens, turkeys, pheasants, quail, domestic ducks, geese and guinea fowl. In another major recent epidemic of the disease, it killed more than 50 million chickens and turkeys in 2014 and 2015, while causing economic losses of $3.3 billion, the USDA estimates. The agency is now researching a potential vaccine against the bird flu.

Fortunately, the public health risk related to bird flu , according to the U.S. Centers for Disease Control and Prevention. Still, cooking all poultry and eggs to an internal temperature of 165 ˚F is advised as a general food safety rule.

The cost of processed eggs — used in liquid or powdered form in manufactured products including salad dressing, cake mix and chips — has also surged, adding to inflationary pressures. 

Inflation cooling

The Consumer Price Index — a closely watched inflation gauge — rose 6.5% in December from the previous year. That was the smallest annual increase since October 2021, the Labor Department  Thursday and continues the steady decline in price increases since they peaked at 9% in June of last year. Falling prices for energy, commodities and used cars offset increases in food and shelter.

But if eggs remain pricey, Chicago resident Kelly Fischer said she will start thinking more seriously about building a backyard chicken coop because everyone in her family eats eggs.

"We (with neighbors) are contemplating building a chicken coop behind our houses, so eventually I hope not to buy them and have my own eggs and I think the cost comes into that somewhat," the 46-year-old public school teacher said while shopping at HarvesTime Foods on the city's North Side. "For me, it's more of the environmental impact and trying to purchase locally."

Eggs are just one of a number of food staples that skyrocketed in price in 2022. For example, margarine costs in December surged 44% from a year ago, while butter rose 31%, according to the CPI data.

—The Associated Press contributed to this report