If you say so then it must be so.  However in my experience many of the really destructive poultry diseases are spread either through the rooster's semen fluid, harbored by the hen, or contracted at hatching from infected equipment, or premises.  You know there must be a reason that fertile eggs are used as a medium in which to culture viruses and bacteria.  But As I always say, those birds belong to you.  Do what you think is best for the greatest number of chickens.  
Started in the 1930s, the control of the spread of communicable diseases is the whole point of the National Poultry Improvement Program.  In fact the NPIP for years and years was only concerned with the control and spread of Pullorum Disease, historically the most destructive chicken ailment on Planet Earth. Pullorum also goes by the common name Pasty Butt or the old scientific name of Bacillus White Diarrhea.  Most losses occur before 3 weeks of age, often the losses are a failure to hatch or thrive but loses in chicks can go as high as 100%.  Coccidiosis and Mareks Disease are two other serious chicken diseases that mostly infect chicks or the young bird.  In carrier hens her ovaries are the only part of the body involved.   
thepoultrysite.com/diseaseinfo/131/salmonella-pullorum-pullorum-disease-bacillary-white-diarrhoea
http://ww.cfsph.iastate.edu/Factsheets/pdfs/fowl_typhoid.pdf
Read up on the clinical signs