One reason that there is no proven cure or vaccine for Ebola hemorrhagic fever is the wiliness of crossover diseases. These viruses are transmitted from animal populations, which can act as reservoirs where the pathogens can develop and mutate, making it difficult for researchers to keep pace with the diseases’ variations.
埃博拉出血热之所以没有行之有效的治疗方法或疫苗是因为传染性疾病大多非常狡猾。病毒的传播起源于动物种群，而动物体就像病原体发展变异的蓄水池。研究人员因此很难跟上传染病的变化速度。