US egg producers are repopulating flocks lost to the outbreak of H5N2 highly pathogenic avian influenza in the spring, while also increasing biosecurity measures ahead of the fall migratory bird season, said Chad Gregory, president and chief executive officer of United Egg Producers.

“Egg farmers affected by A.I. this spring have been working diligently and are making good strides toward resuming egg production,” Gregory said. Some of the producers affected by the earliest outbreaks are beginning to bring young hens back, but it will be at least 12 to 18 months before egg production returns to full, pre-A.I. levels, he said, adding that farms must meet stringent cleaning and disinfection regulations defined by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service before repopulating.

It may take up to 80 weeks to fully repopulate farms because the age of hens is purposely staggered to produce the right amount of eggs to meet customer needs on an ongoing basis, U.E.P. said. A short supply of pullets is adding to the challenge of repopulating flocks. Pullets typically are moved into layer barns when they begin to consistently lay eggs at 16 to 18 weeks of age. A.I. also was detected on some breeder and pullet farms, which reduced the number of birds available early in the repopulation process, U.E.P. said. One breeder hen provides the equivalent of 120 chicks.

The spring A.I. outbreak was the worst in US history, affecting 223 operations and resulting in the loss of more than 48 million birds in 15 states, including about 40 million chickens, mostly laying hens for the processing egg industry, about 8 million turkeys and certain other birds. The virus was introduced by migratory birds flying north in the spring. There is considerable concern about reinfection as birds migrate south this fall.

US egg farms have enhanced biosecurity measures to further protect flocks, including increasing protocols for controlled movement of workers, birds, vehicles and equipment; ensuring feed and water are not at risk; and limiting contact with domesticated and wild birds.

U.E.P. reviewed and summarized chapters of biosecurity recommendations from APHIS for its members, and the American Egg Board distributed biosecurity enhancement recommendations to all commercial egg producers. Increased biosecurity has ranged from minor procedural shifts to large investments in equipment and facilities, U.E.P. said.

“We pledge our best efforts to overcome this setback and rebuild a healthy and viable egg industry,” Gregory said. “It is vital that we continue to work diligently and collaboratively to protect the health and well-being of our flocks, egg farms and rural communities.”