当实验室活动涉及致病性生物因子时，实验室对微生物的致病性和毒力应从哪几个方面进行评估？
参考答案：
对致病性生物因子的致病性和毒力的评估应从：①宿主范围②所引起疾病的发病率和死亡率③疾病的传播媒介④动物体内或环境中病原的量和浓度⑤排出物传播的可能性⑥病原在自然环境中的存活时间⑦病原的地方流行特性⑧交叉污染的可能性⑨获得有效疫苗、预防和治疗药物的程度等。
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It is cool but usually sunny. Sometimes we 3_____________ basketball or 4_____________. Winter starts in 5_____________. The days are short and the nights are long. It is cold and 6_____________. Sometimes it 7_____________ and the 8_____________ is all white. It's very beautiful. We are in warm 9_____________. We often 10_____________ skiing or skating. |