<prompt> Communicability of disease is assessed by?Secondary attack rateGeneration timeSerial intervalIncubation period  <response>: Secondary attack is defined as the number of exposed persons developing the disease within the range of incubation period following exposure to primary case. It is useful in detecting whether a disease of unknown etiology is communicable or not and in evaluating the effectiveness of control measures such as isolation and immunization. Ref: 25th edition, Parks Textbook of Preventive and Social Medicine, Page no. 108 