Cause of antigenic drift in influenza viral infections is: (A) Small mutation in neuraminidase and hemagglutinin, (B) Large mutations in hemagglutinin only, (C) Step mutations in viral genome, (D) None of the above
Answer is A. antigenic drift - small changes in the genes of influenza viruses that happen continually over time as the virus replicates.Antigenic shift - an abrupt, major change in the influenza A viruses, resulting in new hemagglutinin and neuraminidase proteins in influenza viruses that infect humans.