Influenza in New Zealand Before 1918: A Preliminary Report.

In the present article, I aimed to test the hypothesis that possible fatal immunological reactions to the A/H1N1 virus of the 1918 "Spanish" influenza pandemic were the result of previous exposure to the A/H3N8 virus of the 1890-1892 "Russian" influenza pandemic. Using newspapers and official death records to reconstruct mortality peaks from influenza and excess pneumonia deaths in New Zealand before 1918 enabled comparisons with peaks of influenza mortality by age in 1918 from individual death records. For males, mortality peaks in the 1885, 1890-1892, 1894, and 1898 influenza outbreaks appeared to match those from the 1918 pandemic. For females, peaks of deaths in 1918 corresponded to those from the influenza outbreaks of 1887 and 1890-1892. The highest mortality rates for both sexes were among those 28-32 years of age. Although they lend strong support to the hypothesis of fatal immunological reactions derived from early exposure to a different influenza virus, the results from this study also raise more questions: Given that the A/H1N1 virus of 1918 was exceptionally virulent, why did so few children 5-15 years of age die from it? Influenza normally kills only the very young and the very old. In addition, why did twice as many European males as females die in the young-adult age groups, whereas Māori males and females died at almost identical rates?