There seems to be no end to the virulent Newcastle Disease outbreak in California. There were 26 new confirmed cases in one week, most in Riverside County, California. They include backyard exhibition chickens, backyard hobby turkeys, and a retail feed store. Previous positive locations include backyard, non-commercial layer chickens, commercial table egg layers, backyard exhibition birds (which is presumably more than just chickens), commercial table egg pullets, a backyard mixed flock of exhibition birds, and a live bird market. There is no indication of which feed stores had positive chicks or where those chicks came from since no hatcheries appear to have tested positive.
For more information on virulent Newcastle disease, see the article at https://poultry.extension.org/articles/poultry-health/common-poultry-diseases/newcastle-disease-in-poultry/
For ways to protect yourself, see the article on biosecurity at https://poultry.extension.org/articles/poultry-health/biosecurity-for-small-poultry-flocks/