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A security guard wearing a mask stands on a street in Dakar, Senegal, Feb. 25, 2020. The city saw a sand and dust storm Tuesday. (Photo by Louis Denga/Xinhua)

A security guard wearing a mask stands on a street in Dakar, Senegal, Feb. 25, 2020. The city saw a sand and dust storm Tuesday. (Photo by Louis Denga/Xinhua)