<prompt> True about the epidemiology of influenzaIncubation period 10-12 hrsExtra human reservoir not seenPandemics occurAsymptomatic see rarely  <response>: The incubation period is 18-72 hours.Major reservoir of influenza viruses exists in animals and birdsOccur in pandemics every 10-40 years.During pandemics, attack rates tend to be high 5-10 in adults, 20-30 in children.Infects all ages and sexes. Park 23e pg: 147 