Here's why eggs might not be on store shelves right now

Bird flu is spreading across the United States, causing egg prices to soar and availability to plummet.

Cases of bird flu, or avian influenza, have increased among animals -- including dairy cows, wild birds, poultry and even pet cats.

More than 150 million poultry birds have been killed across all 50 states since 2022 in an attempt to combat a strain of bird flu known as H5N1, and those efforts are now leaving grocery store shelve empty where cartons used to sit.

MORE: Egg prices may increase up to 20% as top farm tests positive for bird flu: USDA

The number of birds affected by the virus has been rising in recent months, with roughly 7 million affected in November, 18 million in December, and 23 million in January, according to the latest figures from the U.S. Department of Agriculture.

Over the last 30 days, 125 flocks were confirmed to test positive for bird flu, according to the USDA's Animal and Plant Health Inspection Service. Of the flocks, 81 were on commercial farms and 44 were backyard flocks.

Once a bird is infected, the only way to stop the virus from spreading further is to de-populate or cull the entire flock. This can affect the price of eggs.

David Ortega, food economist and professor at Michigan State University, told ABC News that when a flock that used to lay eggs is culled, it can take time to get a new flock to start laying eggs again.

"Whenever you have a detection, you have to depopulate birds within a given area, and it takes a significant amount of time … to sort of rebuild that flock and for those layers to become productive again," he said. "There's a bit of a biological constraint to this. Producers can't just start producing eggs again if there's quite a bit of a lag."

Ortega said the significant rise in the price of eggs can be tied to increased demand, especially because there aren't many effective substitutes for eggs.

However, he said he doesn't think the U.S. is experiencing a shortage.

"It's not that we have run out of eggs. It's just that, because of the impacts that the bird flu has on the industry and just the way that the supply chains for these products are built, there might be stock outs in certain regions across the country," Ortega said.

Earlier this week, Waffle House, a restaurant chain with over 2,000 locations, implemented a 50-cent surcharge per egg given the unprecedented rise in egg prices.

MORE: Egg prices may increase up to 20% as top farm tests positive for bird flu: USDA

The limited supply of eggs is even leading some to resort to theft. About 100,000 eggs were stolen from the back of a trailer in Antrim Township this past weekend, with a retail value of about $40,000, according to Pennsylvania State Police.

Ortega said he expects to see egg prices continue to increase until the number of cases of bird flu starts falling.

"So many commercial operations have been impacted and we really need a period -- like a sustained period of a number of months where we don't see the level of bird flu impacts that we've been seeing recently -- for things to start to sort of stabilize," he said. "But if we were to have four to six months of no major impact on commercial operations, then we would start to see the price decrease."

As consumers keep their eyes on the egg aisle at their local stores, the USDA announced on Wednesday that a strain of bird flu that had been primarily spreading in wild birds was detected in dairy cattle in Nevada.

This is the first detection of this strain of bird flu, known as D1.1, in cattle. The detection was a result of the USDA’s national milk testing program that launched in early December.

The USDA did not immediately return ABC News' request for comment.

Egg affordability is just one of the concerns arising in connection to the avian flu's ongoing surge; human cases of bird flu have also recently emerged, largely among dairy farm and poultry farm workers.

Human cases have been diagnosed across the country since April 2024, with 67 confirmed in 10 states as of Wednesday, according to the Centers for Disease Control and Prevention.

Most human cases have been mild, with patients fully recovering. So far, just one death has been recorded in Louisiana in a patient over age 65 who had underlying medical conditions. He, and a few of the more severe cases, had contracted the D1.1 strain.

The CDC and other public health officials say there is currently no evidence of human-to-human transmission and that the risk to the general public is low.

Here's why eggs might not be on store shelves right now originally appeared on abcnews.go.com