(Bloomberg) -- Eggs will get even more expensive after US production plummeted to a seven-year low during one of the worst-ever bird flu outbreaks.

The price for eggs is set to rise as much as 21% compared to a year ago, the biggest increase among all food staples tracked by the US Department of Agriculture. In April, the outlook was for an increase of 6% to 7%. 

The outbreak of avian influenza has affected more than 38 million birds in the US, driving both the number of egg-laying birds and the production of table eggs down to the lowest level since 2015, the last time the bird flu virus ran rampant in the poultry industry.

Read More: Bird Flu Outbreak Sends US Egg Output Tumbling to Seven-Year Low

Costs for fats and oils are also rising, as the USDA raised the price estimate to as much as 11% over the past year.

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