Virgin-soil epidemics are those in which the populations at risk have had no previous contact with the diseases that strike them and are therefore immunologically almost defenseless.

处女地流行病指的是那些风险人群以前没有接触过袭击他们的疾病，因此在免疫上几乎毫无防御能力的疾病。

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You also can choose from an array of strike prices and expiration dates depending on your appetite for risk.

你还可以从一系列行权价格和到期日中做选择，具体取决于你的风险承受意愿。

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The gamblers and risk-takers turned south on the California Trail over the Sierra Nevada, ready to strike it big or not at all.

而赌徒和冒险家却在岔路口拐向南方走上了加州小道，翻越内华达山脉，准备好要么发大财要么一无所有。

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Stop Teacher Strikes identifies 110 school districts in Pennsylvania that are currently under immediate risk of strike -- and more than 100 more whose contracts will expire by next summer.

WSJ: Striking Against Students

The search continues amid the endless threat that the helicopters which fired the original rockets may strike again and the risk that the building's half-filled second floor might cave in entirely.

CNN: Baby survives as family dies in Syrian onslaught

Research from Vanguard found that semiannual rebalancing can strike a reasonable balance between risk control and cost minimization.

FORBES: Is Now The Time To Lock In Profits?