US stock futures fell more than 1% in London, while government bond yields slid as investors assessed the impact of the president’s illness and quarantine for financial markets.

Investors, who have driven a long rise in global equity markets, were already nervous given the lack of progress on more US fiscal stimulus.

Stock market volatility gauges rose, with the widely-watched VIX index up to nearly 29 points, from around 27 points on Thursday.

“The President of the US has got a disease which kills people. People are de-risking because of that,” Chris Weston, head of research at Pepperstone in Melbourne, said.

Trump’s diagnosis comes at a particularly sensitive point in the election after this week’s acrimonious presidential debate.

“This does damage Trump’s ability to campaign and time is running out before the election,” Ayako Sera, market strategist at Sumitomo Mitsui Trust Bank in Tokyo, said.

Meanwhile, yields on 10-year US Treasury bonds fell more than 1 bps to 0.66%, just above a one-month low, a classic signal of investors seeking so-called safe havens.

Risk aversion was evident in the currency markets, with the Chinese yuan traded offshore under particular pressure.