Unlike most seasonal influenza virus strains, the 1918 H1N1 strain was anti-Darwinian: Rather than claiming the old, the infirm, and very young children—those with weak or underdeveloped immune systems—this one killed off the strongest and fittest, as well as pregnant women, in disproportionately high numbers, causing a “cytokine storm” in healthy individuals, as we described in chapter 5.
