[Influenza and death. High mortality not only due to the great epidemics]

Abstract

Excess mortality in a population is one of the hallmarks of an influenza epidemic. Apart from the pandemic years, 1918-1919, 1957 and 1968-1969, annual excess mortality has occurred 16 times in Sweden during the period 1911-1988. An unusually high mortality was caused by Influenza A Sichuan 2/87 (H3N2), the unexpected appearance of which at the beginning of November 1988 started an intensive epidemic in Sweden, while other European countries had a relatively mild influenza season. Swedish deaths in December totalled 10,500-2,200 more than expected; age groups over 65 years accounted for 95 per cent of the mortality, and those over 80 (N = 350,000 in Sweden) for 1,400 deaths. 0.4 percent of those over 80 died. The excess mortality is to be explained by the high proportion of the elderly in the Swedish population and the very low rate of influenza vaccination before the outbreak. As the increase in the proportion of the very elderly can be expected to continue, future influenza epidemics will result in even higher mortality unless adequate prophylactic measures are taken.