Mortality Risk Factors for Pandemic Influenza on New Zealand Troop Ship, 1918

We describe the epidemiology and risk factors for death in an outbreak of pandemic influenza on a troop ship Mortality and descriptive data for military personnel on His Majesty s New Zealand Transport troop ship Tahiti in July 1918 were analyzed along with archival information Mortality risk was increased among persons 25-34 years of age Accommodations in cabins rather than sleeping in hammocks in other areas were also associated with increased mortality risk (rate ratio 4 28 95% confidence interval 2 69-6 81) Assignment to a particular military unit the field artillery (probably housed in cabins) also made a significant difference (adjusted odds ratio in logistic regression 3 04 95% confidence interval 1 59-5 82) There were no significant differences by assigned rurality (rural residence) or socioeconomic status Results suggest that the virulent nature of the 1918 influenza strain, a crowded environment and inadequate isolation measures contributed to the high influenza mortality rate onboard this ship