A deadly outbreak of avian flu has wiped out nearly half of the egg-laying hens in the U.S., leaving grocery store aisles empty, driving up prices and forcing retailers to limit purchases to curb hoarding.

Trader Joe’s and other grocers are limiting the number of eggs customers can buy across the U.S., citing limited supply caused by the ongoing bird flu outbreak.

Some grocers are taking steps to stretch their existing egg supplies, the USDA found. It comes as the bird flu has caused egg prices to soar.