But he adds that such large losses to a population are not unusual in epidemics. 但他同时指出，如果考虑到流行病，如此大规模的种群消失就习以为常了。
Now that the epidemics which water-borne diseases can cause are understood,water supplies are organized to prevent them. 既然已经了解到水传播的疾病能引起流行病，人们就组织好供水的工作以防止流行病的发生。
