Man has always fought man. Thoughout history, millions of lives have been lost through war. But this is dwarfed by the number of lives lost to infectious diseases such as the Black Death, cholera, flu and typhus epidemics. In most of history's biggest plagues and epidemics, the improving levels of health and sanitation have ended many once common diseases. But there are still millions lost today to newer plagues, and the spectre of an incurable virus, like the one that wiped out millions in 1918, still looms.