Birds of all ages are susceptible to infection but the clinical signs may vary. The first recognized and most conspicuous signs are the respiratory signs, hence the name Infectious Bronchitis. However, the pathogenicity of the virus for the oviduct in very young chicks or birds in production is often more important. The kidneys may also be affected.
Comparison of normal eggs (above, left) with shell-less eggs (above, right), rough-shelled egg (centrer, and misshapen eggs (bottom) laid by hens during an outbreak of IB.
Young chicken showing respiratory signs.