This story was updated at 1:21 p.m. ET to reflect the rising number of hens affected by the avian flu.

Grocery shoppers throughout the country are finding empty egg shelves at their local market. 

The highly pathogenic avian influenza has caused shortages and price spikes in states such as California, Illinois and Massachusetts. The wholesale price for a dozen large eggs in California reached almost $9 in late January compared to under $6 in early December.  The retail price for a dozen large eggs jumped from about $2.52 in January of last year to nearly $4.15 in December, the latest available from the Bureau of Labor Statistics.

Over the past several years, egg prices have been in flux. There was a large bird flu outbreak starting in early 2022, followed by a much bigger outbreak later that year, said Daniel Sumner, a professor of agricultural and resource economics at the University of California, Davis.

These rising egg prices have put a strain on both consumers and restaurants.

While this disease has been around for a long time, it hasn’t gone away this round, Sumner said. Since 2022, more than 156 million birds have been affected by the virus. In October 2024 alone, HPAI led to the loss of 2.8 million hens in Utah, Oregon and Washington.

“The avian influenza has repeatedly come back after the summer, and it’s being carried on migratory birds,” said Mike Persia, a professor of poultry sciences at Virginia Tech. “That’s what’s reintroducing it each winter.”

This latest round of the avian flu has hit more cage-free hens, Sumner said. Multiple states mandate that eggs can only come from cage-free hens, including California, Colorado, Massachusetts, Oregon, Rhode Island, Utah and Washington. Consumers aren’t able to purchase cheaper, non-cage-free eggs instead, causing cage-free egg supply to decline even further, and prices to rise.

Egg demand is also higher during the holiday season, which has constrained supply as well, Persia said.