Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection. Influenza pandemics, whether moderate or severe, are remarkable events because of the almost universal susceptibility of the world's population to infection.