Molecular evolution and emergence of avian gammacoronaviruses

► The majority of emerging infectious diseases are caused by RNA viruses. ► Rapid replication, large populations and high genetic diversity lead to new IBV types. ► Genetic diversity in gammacoronaviruses is due to mutations and recombination. ► Rapid evolution of IBV makes this virus extremely difficult to diagnose and control. ► Continuous emergence of new IBV types make it an ideal model to study viral evolution.