Dow futures decline as stock investors worry as President Trump says he tested positive for COVID-19

The stock market appeared headed for a sharp drop early Friday after President Donald Trump said he and his wife, Melania, had tested positive for COVID-19.

Dow futures – which predict how the Dow Jones Industrial Average will move when the market opens for trading in the morning – fell 401 points, implying an opening decline of about 406.

Similarly, futures connected to the Nasdaq and S&P 500 signaled sharp drops.

It was not immediately clear why investors were jittery at the news, but it's conventional wisdom in the markets that investors don't like uncertainty.

The Dow closed up 0.1% to 27,816.9 points on Thursday, so a drop of 406 points would equal a decline of 1.5%.

To be sure, a temporary drop or increase in stock futures can also reverse directions quickly.

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In the late hours of Election Day in 2016, futures fell sharply as investors digested the likelihood that Trump would pull an upset victory over Democrat nominee Hillary Clinton.

But stocks ended up reversing direction and rose in the first full day of trading after Trump was declared the winner.

Follow USA TODAY reporter Nathan Bomey on Twitter @NathanBomey.

This article originally appeared on USA TODAY: Trump tests positive, plans quarantine: Dow futures decline