For example, Salmonella is transferred from the hen to the egg by the ovary, long before the shell is even formed around the egg. Then there's the possibility that the Salmonella bacterium could be on the outside of the egg and poor hand washing techniques cause the salmonella to get transferred into the food. Source: http://eatocracy.cnn.com/2010/08/24/why-theres-salmonella-in-your-eggs/ Page 4 of 12, first sentence: http://www.fsis.usda.gov/oppde/rdad/FRPubs/04-034N/Hazard_Identification.pdf Better to be safe than sorry in this. This is how Salmonella continues in flocks. Otherwise it wouldn't pass from the hen to the chick.