Deaths from bacterial pneumonia during 1918-19 influenza pandemic

Abstract

Deaths during the 1918-19 influenza pandemic have been attributed to a hypervirulent influenza strain. Hence, preparations for the next pandemic focus almost exclusively on vaccine prevention and antiviral treatment for infections with a novel influenza strain. However, we hypothesize that infections with the pandemic strain generally caused self-limited (rarely fatal) illnesses that enabled colonizing strains of bacteria to produce highly lethal pneumonias. This sequential-infection hypothesis is consistent with characteristics of the 1918-19 pandemic, contemporaneous expert opinion, and current knowledge regarding the pathophysiologic effects of influenza viruses and their interactions with respiratory bacteria. This hypothesis suggests opportunities for prevention and treatment during the next pandemic (e.g., with bacterial vaccines and antimicrobial drugs), particularly if a pandemic strain-specific vaccine is unavailable or inaccessible to isolated, crowded, or medically underserved populations.

Figure 1

Percentage distributions of fatal cases of influenza–pneumonia during 1918–19 influenza pandemics, by estimated days of illness before death. A) Influenza–bronchopneumonia, Cook County Hospital, Chicago, Illinois, USA (n = 599) (estimated from chart 2 in [19]). B) Australian Imperial Forces, 1918 (n = 972) (G.D. Shanks, unpub. data). C) General population, Prussia (n = 6,223) (22). D) US Army autopsy series (n = 94) (estimated from supplementary Figure 2 in [17]). E) Influenza with secondary staphylococcal pneumonias, Fort Jackson, South Carolina, USA (n = 153) (interpolation of data in Table 1 in [21]). F) New South Wales, Australia (n = 3,866) (20). G) US Army training camp, Camp Pike, Arkansas, USA (n = 234) (5). Horizontal bars indicate interquartile ranges; vertical lines indicate medians.

Figure 2

Cumulative percentage deaths from influenza–pneumonia, by days (estimated) from illness onset, among fatal cases during various epidemics, 1918–19 (,–22). Vertical arrows indicate median no. days to death.

Figure 3

Cumulative percentage deaths by days of pneumonia, in relation to days of illness before pneumonia, among 234 US Army soldiers who died of influenza–pneumonia at Camp Pike, Arkansas, USA, autumn 1918 (5).

Figure 4

A) Influenza–pneumonia-related morbidity and mortality cumulative incidence rates, in relation to status on troop ships, Cruiser and Transport Service, US Navy, 1918 (9). B) Influenza–pneumonia mortality rates for white men, by employment as coal miner versus other industrial occupation, and by age group, October–December 1918 (6).

Figure 5

A) Estimated age group–specific influenza case rates (15,16). B) Estimated age group–specific pneumonia rates and mortality rates, based on household surveys of 10 communities throughout the United States (15,16).