Epidemic influenza is distinguished from pandemic influenza because it is less virulent. It also has a lower attack rate, one that varies from 10% to 20%. By August 1957 there had been eight major flu epidemics. The first one occurred in 1580. It moved westward from Asia and infected Europe. A pandemic began in China in the fall of 1781-1782. Before spreading throughout Europe, it occurred nearly simultaneously in Siberia and Russia. The second wave of influenza pandemics usually attack greater numbers of victims. It is generally more severe than the first wave and is accompanied by harsher complications.