Researchers have stressed that bird flu still poses a minimal risk to the general public, though that may change as the virus continues to circulate and potentially mutate. But the many empty shelves in stores and higher prices on the eggs that people can find have raised concerns among consumers about the safety of the egg supply.

Waffle House announced it will be adding a $0.50 surcharge to all egg items on the menu sold at its more than 2,000 locations because of soaring egg prices caused by the bird flu. The surcharge went into effect Monday.

Thieves in the US state of Pennsylvania have stolen more than 100,000 eggs - worth $40,000 (£32,000) - from a single grocer. The heist targeted the back of a lorry at Pete & Gerry's Organics in Greencastle on 1 February,