The conditions the chickens are kept in. Normally you can buy factory farm eggs ($2-3/dozen), cage-free eggs ($3-6/dozen) where the chickens can still be kept indoors, or free-range eggs ($6-10/dozen) where the chickens get to forage in a pasture of some sort. The factory farm conditions are what causes such rapid transmission so the only farms left are the smaller ones.
The conditions the chickens are kept in. Normally you can buy factory farm eggs ($2-3/dozen), cage-free eggs ($3-6/dozen) where the chickens can still be kept indoors, or free-range eggs ($6-10/dozen) where the chickens get to forage in a pasture of some sort. The factory farm conditions are what causes such rapid transmission so the only farms left are the smaller ones.