Relative mortality ratio (RMR) across age groups. The RMR is the ratio between the percentage of influenza deaths in a given age group and the percentage of all-cause deaths in the same age group. The age distribution of mortality due to influenza were established from the report of 368 influenza deaths during the 1978-79 seasonal epidemic and 1,926 influenza deaths during the 1989-90 seasonal epidemic in the US. The age distribution of mortality due to influenza were obtained from the report of 508 (1988-89) and 1,990 (1989-90) influenza deaths in France. Pandemic age-distribution were obtained from 308 (France) and 6,317 (US) influenza deaths.