It's an exceedingly common disease that is passed down vertically, that is, from egg to chick, nearly synonymous with meat birds. It's one of the more genuine factors that prevent the vast majority Cornish Crosses from surviving past fifteen weeks. Moreover, it is nearly impossible to vaccinate for as there are so many different antibiotic resistant strains. Symptoms generally won't appear until after the 12th week or so and many homesteaders and small farmers are experiencing a real tragedy at their USDA processing (slaughter houses) facilities as the birds which appear symptomatic for the disease, ( all internal) are condemned. Even more disconcerting is the fact that a very large number of commercial layers, Buff Orpingtons and the new super layer strains will often also test positive for the disease, with their immune systems succumbing in their second-fourth years It's so common that it borders on the alarming.