If the virus had been capable of spreading through the air, or if one infected person had unknowingly entered a large population center, Ebola might have become a worldwide epidemic.
出自-2013年6月聽力原文
柯林斯高階英漢雙解學習詞典釋義
ADV
未意識到地；不知不覺地；無意中
If someone does something unknowingly, they do it without being aware of it.
例句
...if people unknowingly move into more contaminated areas of the river.如果人們在不知情的情況下搬到了河流污染更嚴重的地區...the extent to which the workforce colludes knowingly or unknowingly with such criminal activity...在何種程度上職工有意或無意地參與到這樣的犯罪活動中