FREETOWN, Sierra Leone—The crane, the earthmover and several heavy trucks sit idle in the closed compound of China Civil Engineering Construction Co., a still-life portrait showing how Ebola has paralyzed Africa’s biggest investors.

“Nobody gets in,” Li Ning, the company’s chief engineer, said of his company’s self-quarantined compound. Then nodding to what he estimates is a half-year supply of bottled water stacked against an office wall, he added: “And I don’t go out.”

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