Pathogenic responses among young adults during the 1918 influenza pandemic.
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.
Australian Army Malaria Research Institute, Enoggera, Queensland, Australia. dennis.shanks@defence.gov.au
G Dennis
GD
Shanks
John F
JF
Brundage
D000818:Animals; D049672:History, 19th Century; D049673:History, 20th Century; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000150:complications / Q000266:history* / Q000276:immunology / Q000401:mortality; D008954:Models, Biological; D058873:Pandemics / Q000266:history*; D018410:Pneumonia, Bacterial / Q000209:etiology / Q000266:history / Q000276:immunology / Q000401:mortality