Abstract
Of the unexplained characteristics of the 1918-19 influenza pandemic, the extreme mortality rate among young adults (W-shaped mortality curve) is the foremost. Lack of a coherent explanation of this and other epidemiologic and clinical manifestations of the pandemic contributes to uncertainty in preparing for future pandemics. Contemporaneous records suggest that immunopathologic responses were a critical determinant of the high mortality rate among young adults and other high-risk subgroups. Historical records and findings from laboratory animal studies suggest that persons who were exposed to influenza once before 1918 (e.g., A/H3Nx 1890 pandemic strain) were likely to have dysregulated, pathologic cellular immune responses to infections with the A/H1N1 1918 pandemic strain. The immunopathologic effects transiently increased susceptibility to ultimately lethal secondary bacterial pneumonia. The extreme mortality rate associated with the 1918-19 pandemic is unlikely to recur naturally. However, T-cell-mediated immunopathologic effects should be carefully monitored in developing and using universal influenza vaccines.
Highlights
Of the unexplained characteristics of the 1918–19 influenza pandemic, the extreme mortality rate among young adults (W-shaped mortality curve) is the foremost
We present hypotheses that are scientifically credible, consistent with the historical record, and account for epidemiologic and clinical manifestations of the pandemic
If the first 2 epidemic waves of the 1918–19 pandemic were caused by the same or immunologically cross-reactive influenza A (H1N1) viruses, persons affected during the first wave should have been protected from infection and, in turn, illness, secondary pneumonia, and death during
Summary
Of the unexplained characteristics of the 1918–19 influenza pandemic, the extreme mortality rate among young adults (W-shaped mortality curve) is the foremost. Before 1918, most members of the 1875–1900 birth cohorts had been exposed to the 1889–90 pandemic influenza strain These persons were 18–43 years old, the age groups at highest mortality risk, during the lethal second wave of the 1918 pandemic [20]. If the first 2 epidemic waves of the 1918–19 pandemic were caused by the same or immunologically cross-reactive influenza A (H1N1) viruses, persons affected during the first wave should have been protected from infection and, in turn, illness, secondary pneumonia, and death during. Similar observations were made in other groups of military and civilian health care workers [21] These findings suggest that the occupational group with the most intensive exposure to the pandemic strain had relatively low influenza-related pneumonia mortality rates during the second wave [12]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call