大范围流行，死人甚多的传染病被人们称作瘟疫。据初步统计，全球危害性较大的传染病有50种以上，20世纪人类平均寿命从40岁延长到60多岁，这是人类与“瘟神”搏斗的重大成果之一。虽然20世纪初危害最大的鼠疫，霍乱，斑疹伤寒目前已受到有效控制，但流感，传染性肝炎，疟疾， Popular epidemics, many deadly infectious diseases are called plagues. According to preliminary statistics, there are more than 50 infectious diseases with a great danger in the world. The average life expectancy of people in the 20th century was extended from 40 to over 60 years of age. This is one of the major achievements of the struggle between humans and the “plague god.” Although the most harmful plague, cholera and typhus at the turn of the twentieth century have been effectively controlled, influenza, infectious hepatitis, malaria,