细菌性痢疾在卫生条件不良,文化经济不发达的地区,时常可发生比较大的流行。同一地区的不同年份发病率的动态变化差异较大,由于存在偶然变动,因而不能正确地判断发病率增高或下降的趋势,从而对观察疾病在不同年份发病的动态变化带来了某些影响或偏差。笔者根据杭州市1970 Bacillary dysentery in the poor health conditions, cultural and economic underdeveloped areas, often can occur relatively large epidemic. The dynamic changes of morbidity in different years in the same area are quite different. Due to the occasional change, the trend of increasing or decreasing morbidity can not be correctly judged, which has some impact on the observation of the dynamic changes of morbidity in different years or deviation. The author based on Hangzhou 1970