It affects chickens of all ages, types, and breeds. The disease is caused by a coronavirus which is known to have a high mutation rate. The arrival of new IB variants poses a continuous problem for the poultry industry. The virus enters the body by the inhalation or conjunctival route.
Infectious bronchitis is considered to be a highly contagious respiratory disease.
Characteristically accompanying the disease are mild respiratory signs such as sneezing, snicking, gasping, and a watery discharge from the eyes and nostrils. In the respiratory tract, clear mucus and areas of inflammation are present. The mucus tends to accumulate in the lower part of the trachea and a mucus plug is sometimes found near the bronchi. Normally, if the virus spreads through the flock, all of the birds are affected. Many times the IB virus may spread through the flock without producing obvious clinical signs of disease except a mild cough.