The United States is experiencing a persistent egg shortage, prompting Dennys (DENN.US) to impose an egg surcharge.

U.S. chain restaurant Dennys (DENN.US) announced on Monday that it would temporarily charge an extra fee for dishes containing eggs due to a nationwide shortage of the ingredient. The South Carolina-based company stated that the fee would vary from store to store among its roughly 1,500 locations.

"Due to the nationwide shortage of eggs and the increase in egg prices, some of our restaurants will need to temporarily charge an extra fee for each dish containing eggs," Dennys said in a statement. "The fee will vary based on market conditions and restaurant conditions due to the varying effects of the egg shortage in different areas."

Dennys said it would not disclose which areas or stores would be charging the fee due to the "unstable" situation.

The avian flu has killed millions of hens, leading to egg shortages at grocery stores and restaurants across the country. The supply is so tight that wholesale prices have hit record highs.

The U.S. Department of Agriculture said on Friday that the wholesale price of eggs "steadily increased and was high to begin with" due to the flu, and the supply was "very tight and unlikely to improve in the short term."

Prices for white eggs rose 33 cents, or 4.7%, to $8.07 per dozen last week. Overall inventory was down 2%, with cage-free eggs down 3.5% and enriched eggs down 12.5%.

Dennys is not alone in passing on higher costs to consumers. Waffle House decided earlier this month to charge 50 cents for each egg.

Meanwhile, chains like Trader Joe's and Walmart (WMT.US) have limited the number of eggs customers can buy.