U.S. stocks tumbled the most since June with rising virus cases threatening the economic recovery. More than $2 trillion has been wiped from the value of American equities this week and Wall Street’s fear gauge spiked to the highest in four months.

Big tech companies from Apple to Amazon led the rout, their shares having gotten so expensive relative to expected earnings that further price gains became hard to justify. Software giant SAP SE set off alarms on future profit when it warned revenue would suffer well into 2021. A day later, U.S. tech darlings exacerbated market volatility for the second time in two months after a summer of gains that outpaced the broader market’s advance by 10 times.

“There’s uncertainty around the coronavirus surrounding the impact of another wave of shutdowns,” Matt Maley, chief market strategist at Miller Tabak + Co., said by phone. “If one of these other tech companies talks about lockdowns affecting their earnings in 2021 the way SAP did, we’ll have a big problem.”

The S&P 500 fell 3.5% to close at the lowest in five weeks. Tech shares in the gauge sank 4.3%. Alphabet Inc. and Facebook Inc. lost more than 5%. The VIX jumped almost seven points to close above 40.

The worry over future earnings is spiking just as big tech lines up to report results. Investors punished Microsoft Corp. even though its third-quarter profit beat expectations and its forecast was mostly in line with estimates. The stock plunged more than 4%.

Up next are the other four of the market’s five biggest constituents that have a combined $5 trillion in market cap. Apple, Amazon, Facebook and Alphabet all report Thursday after the close. All are expected to show a strong third calendar quarter, but the focus will be on how they see the end of 2020 and the start of next year.

“Because tech has supported the market’s rally in 2020, the earnings of those big tech companies are going to really drive sentiment,” said Chris Gaffney, president of world markets at TIAA Bank. “The risk is that it could drive it in a negative way and add on like a snowball rolling downhill to this selloff.”

Buyers had piled into the tech giants for the safety provided by their strong balance sheets and products that cater to stay-at-home demand. They stayed with them as the economy rebounded because of their size advantage. But with the virus rampaging and Congress unlikely to shore up the economy with an aid package, speculation has mounted that tech earnings won’t be able to meet lofty expectations.

Enormous bubble

That’d be fodder for bears like David Einhorn, who called an “enormous” bubble in tech stocks and said his firm has added bearish wagers. The big top for tech stocks may have occurred on Sept. 2, according to the president of Greenlight Capital, who cited a surge in trading of call options and a growing industry concentration among signs of excessive euphoria. Since then, the tech-heavy Nasdaq 100 has plunged almost 10%.

“Bubbles tend to topple under their own weight. Everybody is in,” Einhorn wrote in an Oct. 27 letter to investors. Greenlight has adjusted the portfolio of companies it’s wagering against by adding a fresh so-called bubble basket of mostly “second-tier companies and recent IPOs trading at remarkable valuations,” he added, without identifying specific stocks.

Usually earnings tend to calm the market during periods of stress. But not this time. Among S&P 500 companies that have disclosed results, 85% beat analyst estimates and are on pace for the best showing since Bloomberg began tracking the data in 1993. That’s doing little to excite buyers who have watched the index rallying as much as 60% from its March trough and valuations reaching levels not seen since the dot-com bubble.

On the contrary, traders are taking profits off the table. As a result, shares of companies in the S&P 500 reporting quarterly earnings have dropped 0.8%, on average, the next day. Tech shares have fared the worst, falling 2.7%, data compiled by Bloomberg showed.

“The stock reaction tomorrow from AMZN, FB, GOOG and AAPL will be telling as to whether tech can keep up this dramatic pace of outperformance,” said Peter Boockvar, chief investment officer at Bleakley Advisory Group, referring to the tickers of the tech giants. “A regime change is at hand as valuations begin to contract.”

Tech firms have yet to prove that the boost in businesses during the pandemic is not fleeting. Microsoft gave a second-quarter forecast for revenue in some divisions that fell short of the highest analysts’ projections. Earlier this month, Intel Corp. reported a surprise drop in sales of chips for data centers, potentially signaling a drop-off in demand for expansion of the server farms that underpin cloud-computing services. Netflix Inc. missed Wall Street’s estimates for subscribers, renewing doubts about its ability to maintain growth as pandemic lockdowns go away and competition intensifies.

“There is no question that these companies have great business models, have executed well and stand to benefit from how the economy is reshaping itself, but there are questions about if they have gone too fast, too far,” Peter Tchir, head of macro strategy at Academy Securities. “Parabolic valuation increases can only be justified by extremely strong guidance. A lot of great companies have seen incredible gains in their stock prices.”