US futures and global markets rattled after Trump tests positive for coronavirus

Dow futures were last down 370 points, or 1.3%, after falling more than 450 points just after Trump tweeted his condition. S&P 500 futures were down 1.3% and Nasdaq futures were down 1.6%.

"Tonight, @FLOTUS and I tested positive for COVID-19. We will begin our quarantine and recovery process immediately," Trump tweeted shortly before 1 a.m. ET Friday. "We will get through this TOGETHER!"

Stocks in Asia Pacific also slid on the news. Japan's Nikkei 225 dropped 0.7%, while Australia's S&P/ASX 200 fell 1.4%. Other markets in the region, including those in Hong Kong, mainland China and South Korea, are closed for public holidays. European stocks opened lower, with the FTSE 100 dropping 0.7% in London, while France's CAC 40 shed 1% and Germany's DAX declined 1.1%.

Oil futures also tumbled. US crude futures fell 2.8% to $37.62 per barrel, while Brent, the world oil benchmark, lost 2.8% to hit $39.79 per barrel. Both had settled lower on Thursday.

"The Trump diagnosis is an immediate negative," said Jeffrey Halley, senior market analyst for Asia Pacific at Oanda, adding that safe haven assets will likely strengthen on the news. The Japanese yen has already surged and was last trading at about 105 yen per US dollar, up 0.4%. Gold prices rose 0.5% to $1,915 per ounce.

US stock futures were already trending lower earlier as the fate of a massive US stimulus plan remained uncertain, and as news broke that top Trump aide Hope Hicks tested positive for the virus.

Before Trump announced his diagnosis, CNN medical analyst Dr. Jonathan Reiner said that Hicks' positive test should be enough to push Trump and his West Wing staffers into quarantine.

"They should all be out of commission, anyone in the West Wing," Reiner told CNN's Don Lemon. "Seriously, the virus doesn't care if you don't take it seriously. It's an incredibly contagious pathogen."

Halley said investors should now be looking out for how far the virus has spread across the US administration.

"Has Covid-19 now spread to the upper echelons of the US Government leadership, including the Senate Republicans?" he said, adding that many are old men and therefore in a high-risk group. "That will be an evolving situation over the coming weekend and will lead to a sustained rotation into defensive positioning if it becomes reality."

— Charles Riley Anneken Tappe and Jazmin Goodwin contributed to this report.