1918 Influenza, a Puzzle with Missing Pieces
Figure. Combined influenza plus pneumonia (P&I) age-specific incidence, mortality, and case-fatality rates, per 1,000 persons/age group, US Public Health Service house-to-house surveys, 8 states, 1918, and US Public Health Service surveys during 1928–1929. A) P&I incidence for 1918; B) mortality rate for 1918 (ill and well persons combined); C) P&I case-fatality rates for 1918 (solid line) compared with a more typical curve of age-specific influenza case-fatality rates (dotted line) from 1928–1929. Reprinted from (3).