Pandemic versus Epidemic Influenza Mortality: A Pattern of Changing Age Distribution

Abstract

Almost all deaths related to current influenza epidemics occur among the elderly. However, mortality was greatest among the young during the 1918-1919 pandemic. This study compared the age distribution of influenza-related deaths in the United States during this century's three influenza A pandemics with that of the following epidemics. Half of influenza-related deaths during the 1968-1969 influenza A (H3N2) pandemic and large proportions of influenza-related deaths during the 1957-1958 influenza A (H2N2) and the 1918-1919 influenza A (H1N1) pandemics occurred among persons <65 years old. However, this group accounted for decrementally smaller proportions of deaths during the first decade following each pandemic. A model suggested that this mortality pattern may be explained by selective acquisition of protection against fatal illness among younger persons. The large proportion of influenza-related deaths during each pandemic and the following decade among persons <65 years old should be considered in planning for pandemics.

The first, second and third wave of pandemic influenza A (H1N1)pdm09 in North Denmark Region 2009–2011: a population‐based study of hospitalizations

“…We present patterns of morbidity and mortality, clinical features, underlying medical conditions, treatment and concomitant and secondary bacterial co‐infections. Finally, we compare our data with observations from previous pandemics 2, 3, 4…”

“…Due to lack of viral assessment of pathogenecity during the waves of 1918–19, it is unclear whether the reported incidences were related to change in virulence, host immune response or other epidemiological factors. Experiences with the two other pandemics of the past century, 1957 and 1968, revealed patterns of varying severity,4 so it is of crucial importance to observe detailed patterns of hospitalization and mortality of any new pandemic strain. However, our results could be supported by recent studies from the US and Spain of a higher mortality of hospitalized H1N1pdm09 patients in the post‐pandemic season 7, 8.…”

1918 Influenza: the Mother of All Pandemics

“…A sharper perspective emerges when 1918 age-specific influenza morbidity rates ( 21 ) are used to adjust the W-shaped mortality curve (Figure 3, panels, A, B, and C [35,37]). Persons <35 years of age in 1918 had a disproportionately high influenza incidence (Figure 3, panel A).…”

The national burden of influenza‐associated severe acute respiratory illness hospitalization in Zambia, 2011‐2014

“…Influenza virus infection is a major cause of severe acute respiratory illness (SARI) and results in significant global morbidity and mortality every year 1, 2, 3. However, the majority of available information on influenza disease burden emanates from industrialized countries.…”