病原体侵入人体后,寄生在机体的某些部位,机体免疫功能使病原体局限化,但不足以将病原体清除,待机体免疫功能下降时,才引起疾病,此种表现称之为( )。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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