Influenza virus causes new epidemic by (3-5 yrs) -
Antigenic variations in Influenza Antigenic shift Antigenic drift Occurs due to Genetic recombination/reassoment / Rearrangement Point mutation Nature Sudden Gradual / insidious May lead to Epidemics/ pandemics Sporadic cases Ref: Park 25th edition Pgno : 166-172
Antigenic drift
Antigenic shift
Cyclic trends
Mosaicsm
Communicable diseases