This is an excerpt from the Merck Vet manual. According to this Coryza is not an egg transmitted disease.
Chronically ill or healthy carrier birds are the reservoir of infection. Chickens of all ages are susceptible, but susceptibility increases with age. The incubation period is 1-3 days, and the disease duration is usually 2-3 wk. Under field conditions, the duration may be longer in the presence of concurrent diseases, eg, mycoplasmosis.
Infected flocks are a constant threat to uninfected flocks. Transmission is by direct contact, airborne droplets, and contamination of drinking water. All-in/all-out management has essentially eradicated infectious coryza from many commercial poultry establishments in the USA. Commercial farms that have multiple-age flocks tend to perpetuate the disease. Egg transmission does not occur. Molecular techniques such as restriction endonuclease analysis and ribotyping have been used to trace outbreaks of infectious coryza.