(Reuters) - U.S. wholesale egg prices are shattering records as an accelerating outbreak of bird flu in laying hens slashes supplies while shoppers buy more to bake Christmas cookies and other holiday treats.

The increases hit consumers already grappling with stubborn inflation and bracing for potentially higher prices on a broad range of items if President-elect Donald Trump follows through on plans to slap tariffs on goods from China and Mexico.

Wholesale prices for large eggs reached $5.57 per dozen in the Midwest on Wednesday, up 150% from a year ago and topping the previous record of $5.46 from December 2022, commodity data firm Expana said.

Prices are even harder to stomach in California, where supplies are further constrained by rules that prohibit farmers from raising hens in cages. There, eggs set an eye-popping record of $8.85 per dozen, Expana said.

Those high prices are a bonanza for farmers who manage to avoid bird flu outbreaks and are not locked in to long-term pricing arrangements that help control costs at some major retailers. But consumers could still suffer.

The average retail price of a dozen eggs exceeded $3.60 in November, up from $2.50 at the start of the year, according to the Bureau of Labor Statistics. Only in September was the average price higher, at $3.80.

FURTHER PRICE RISES POSSIBLE

Retailers have been slow to pass on higher costs, in part because they do not want to scare away shoppers during the busy holiday season, but they may lift prices in the new year, said Karyn Rispoli, Expana's managing editor for eggs.

In an early sign of an impact, U.S. grocery chain Giant, owned by Ahold Delhaize, canceled a promotion planned for January around Washington and Baltimore, said Giant pricing director Erik Weenink.

"We just don't know where costs are going to sit," he said.

The main factor driving egg prices higher is damage to the laying flock from bird flu. The virus has wiped out nearly 123 million chickens, turkeys and other poultry in 49 states since the beginning of the current outbreak in 2022.

Nationwide, the U.S. laying hen flock in October was down 3% from the year prior, at about 315 million birds, and egg production was down 4%, according to the U.S. Department of Agriculture.

USDA this month lowered its forecasts for egg production and exports in 2025 while raising its price outlook.

"There's not enough supply for the export markets, just like there isn't that much of a supply for the U.S. market," said Greg Tyler, CEO of the USA Poultry & Egg Export Council, a trade group.

HUMANS IMPACTED

Of 35 million commercial egg-laying hens killed by bird flu this year, nearly half contracted the virus in the past three months, data shows.

Workers in Iowa, the top egg-producing state, began culling a massive flock of 4.2 million hens that tested positive this month.

"We're in one of those windows where it's just rampant," Rispoli said.

Wild birds can transmit the virus to poultry flocks. This year, outbreaks among cows also increased risks for farm delivery trucks to carry the virus to poultry barns from dairies.

The virus has infected 61 people so far this year, according to federal data. The cases in humans have mostly been mild, though officials confirmed the first severe case this week in Louisiana.

USDA has been funding vaccine research that could be used to protect poultry and cows from bird flu.

Agriculture Secretary Tom Vilsack told Reuters the agency has funds to purchase some of the vaccine and it would be logical for the Trump administration to continue supporting vaccine development.