Live blog: US markets tumble, following Europe lower

Global stock markets continued their rollercoaster ride on Thursday, with U.S. markets falling after the open. Europe markets fell firmly back into negative territory - after initially trading higher - putting pressure on U.S. equities.

Concerns over the health of the European and U.S. economies, and fears over the spread of Ebola, have roiled global markets, resulting in wild swings on Wall Street. Asia also joined the global rout overnight.

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