Those who had suffered from the earlier spring infl uenza generally suffered less discomfort in the second wave which would occur in the early summer of 1918 in Europe, affecting the outcome of the war. The third and most deadly wave of the infl uenza would occur later that year in the late fall. Despite the obvious differences between the strains in each wave, it is suggested that the more virulent form of infl uenza was genetically derived from the spring infl uenza [3, 10, 12] . The antigenic composition of the 1918 virus is related to the H1N1 viral group. Phylogenetic studies indicate that the virus responsible for the 1918 infl uenza and viruses that provided gene segments for the Asian/1957 and Hong Kong/1968 pandemics are still circulating in wild birds, with few or no mutations [10,11,16,] . The extreme virulence of fall 1918 infl uenza strain has been blamed on severe pathology with acute pulmonary edema, as well as hemorrhage with acute bronchiolitis, aveolitis and bronchopneumonia [20] it is believed that the severe infl ammation of the lungs initiated high levels of cytokines resulting in a depletion of neutrophils and alveolar macrophages, causing death. The stronger the host's immune system, the stronger response to the infl uenza infection, and greater release of cytokines to counter the virus [19, 20] . This is what resulted in the much higher than average mortality among the 15-40-year-old cohort. Patterson and Pyle [12] , Crosby [8] and many other researchers believe that a strain of pneumonia bacteria accompanied the virus [3, 12] . Noyes [3, 14, 17] noted that the nation's people were stricken and died from the illness at differing rates, just as the cities were hit at differing rates. There was no correlation between populations, or even geographical demographics. Sex and age both played a major factor in determining the susceptibility to the disease of the individual. Females were stricken in rates greater than males, and young adults were sickened in greater numbers that other age cohorts [3, 13 and 14] .