Futures on American stock indexes tumbled, extending their 13% drop since mid-February, as plummeting oil prices added to the backdrop of dread surrounding the coronavirus outbreak.

The drop erased the rally that lifted cash equities in the final hour of trading on Friday, as crude sank more than 20% in the deepest rout since the U.S.-led war in Iraq in 1991. While energy and commodity stocks only make up about 5% the S&P 500, plunging crude prices exacerbated the blow to investor sentiment from the virus, standing as one of the starker signals to date of the outbreak’s economic toll.

Volatility has been rampant in markets around the world amid an outbreak that has infected 108,000 people and killed more than 3,700. At least 10 billion shares have traded on U.S. exchanges each day for two weeks, gauges of equity turbulence are at nine-year highs and strategists have begun lowering earnings forecasts for the rest of the year.

Contracts on the S&P 500 sank 4.1% as of 7:22 p.m. in New York. The slide reached 4.4%, threatening to trigger Chicago Mercantile Exchange trading rules that limit losses at 5%.

The spreading coronavirus has kept investors on edge for weeks, forcing upon them the near-impossible task of assessing its eventual impact on the global economy. Now, with Saudi Arabia initiating a price war in the oil market, they’ll have to contend with crude prices that are in free fall.

“It is too early to expect a market bottom,” Satya Pradhuman, director of research at Cirrus Research, wrote in a note to clients. “Credit spreads are likely to widen further from here. In addition, earnings risks abound and estimates are still likely to fade further.”

After an OPEC+ meeting in Vienna failed to reach an agreement regarding further oil output cuts, Saudi Arabia said it plans to boost oil output next month to more than 10 million barrels a day. Some strategists see such a move causing oil prices to fall below $30 a barrel, as as deluge of supply combines with a shock to demand.

While the energy sector is now the third smallest in the S&P 500, a change from a decade ago when the industry made up 11% of the benchmark, tumbling oil prices is yet another risk for traders to contemplate.

“If WTI falls into the low $30s and stays there, it’s going to cause lay-offs in the oil patch and stresses in the high yield market -- like it did when oil fell dramatically in 2015,” said Matt Maley, an equity strategist at Miller Tabak & Co.

Credit markets began to show signs of stress last week, as spreads widened and a derivatives index that investors use to hedge against losses surged the most since at least 2011. Meanwhile, Treasury yields fell to record lows, sending worrisome signals over any economic growth outlook. While the Federal Reserve has already issued an emergency interest rate cut, markets are screaming for more.

“Investors will not focus on global stimulus measures, a potential ramp in production from China, the healthy U.S. consumer, aggressive Fed easing, and relatively attractive U.S equities, until they have confidence that the U.S. government and Fed will ‘do what it takes’ to lower tail risk,” Dennis Debusschere, head of portfolio strategy at Evercore ISI, wrote in a note to clients Sunday. “If that happens, the focus will turn to how the outbreak has evolved in China and if the U.S. is on a similar path.”