这种疾病的起因已有完备的记载。
当然了，最好的东西是治疗严重疾病的药。许多科学家正在努力对抗各种疾病，如埃博拉病毒这种可怕的疾病，而非洲已有几千人因此丧命。
Well, of course, the best thing is medicine for really bad diseases (疾病). A lot of scientists are working very hard to stop diseases like Ebola, a terrible disease that has killed many thousand people in Africa.
已有大量文件证明该病毒在人类引起罕见但严重的疾病的能力。
The ability of this virus to cause rare but severe disease in humans is well documented.
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