The Dow Jones industrial average sank 879 points Tuesday as investors absorbed increasingly worrisome forecasts about the coronavirus, which is spreading faster and more broadly than initially thought and is renewing recession anxiety. Tuesday brought the Dow’s two-day swoon to more than 1,900 points — the worst two-day percentage loss in two years.

The blue-chip index went into full retreat after health officials warned it was only a matter of time before the deadly virus becomes a public health threat in the United States. In separate briefings, officials from the Centers for Disease Control and Prevention, the National Institutes of Health, and other agencies adopted a new tone about the outbreak, emphasizing that they no longer viewed its domestic spread in terms of “if” but rather “when.”

“We are finally starting to see the markets react to the coronavirus,” said Nicole Tanenbaum, chief investment strategist at Chequers Financial Management. “There has been a lot of complacency in the market and a sentiment-driven rally that hasn’t taken into account that this virus may not be as contained as we hoped it would be.”

Tuesday’s slide extended Monday’s dismal finish, which saw the Dow shed more than 1,000 points in one of the steepest point losses in history. At the market close Tuesday, the Dow stood at 27,081 after having flirted with 30,000 earlier this month. It has fallen 6.59 percent this week. The broad Standard & Poor’s index closed at 3,128, down 3.03 percent on the day and down 6.28 percent over the past two days. The Nasdaq composite finished the day down 2.77 percent at 8,965.

“Stocks are due for a bumpy ride as the market assesses the growing likelihood of a broad economic downturn,” Ball State University economist Michael Hicks said. “The economic fundamentals of recession in China and the increasing risk of covid-19 clearly point to more losses. This is not just a few spooked investors.”

Global markets also have trembled as the outbreak intensifies outside China. Japan’s Nikkei index sank more than 3 percent. The Shanghai Composite Index was down roughly 0.6 percent, and Hong Kong’s Hang Seng was essentially flat. In Europe, Britain’s FTSE 100 fell 1.94 percent, and Germany’s DAX closed the day down 1.88 percent.

The price of oil was hit hard, with U.S. benchmark West Texas Intermediate dipping below $50.

“This is the make-or-break point trying to make a profit in the shale oil patch,” said John Kilduff of Again Capital.

Kilduff said the cratering of demand from China and South Korea “is a one-two punch to demand. You now have two out of three Asian economies throttling down the manufacturing and oil demand. It’s a major hit.”

Meanwhile the yield on the 10-year Treasury note, a key benchmark, fell to 1.32 percent during the day as investors fled to safety amid growing alarm that the global economy is pulling back. Yields drop as the price of bonds rises.

“It’s fear,” said Michael DePalma, a managing director at MacKay Shields. “Treasurys are all about fear. And right now you are seeing fear that coronavirus infects more of the world, and the economic ripple effects are going to be severe. Investors are anticipating a global economic slowdown, so they are going to the safest, most liquid investment in the world. That’s U.S. Treasurys.”

Larry Kudlow, the president’s top economic adviser, said he thinks long-term investors should buy stock and expressed optimism that the Chinese economy could rebound quickly.

“We have contained this. We have contained this. I won’t say airtight, but pretty close to airtight,” Kudlow told CNBC.

Kudlow also said he did not expect the Federal Reserve to react to the coronavirus and cut interest rates to juice the economy. He said there is “no supply disruption” yet appearing in the numbers that the White House is studying.

The pneumonia-like illness has spread rapidly since emerging in late December, with China confirming more than 77,650 cases and more than 2,660 deaths to date. Iran has confirmed 95 cases and at least 15 deaths. And South Korea reported 144 new cases, bringing its total to 977.

Shares of Moderna, a Massachusetts-based drugmaker, surged 25 percent Tuesday on reports that it had shipped the first batch of an experimental coronavirus vaccine to U.S. government researchers.

According to the Wall Street Journal, Moderna had sent vials to the National Institute of Allergy and Infectious Diseases in Bethesda, Md. The institute told the Journal that it expects to start a clinical trial of 20 to 25 healthy volunteers by the end of April.

Much is still unknown about the novel coronavirus, prompting a rush to produce a vaccine and test its safety and efficacy. That push isn’t coming only from private biotech firms. Late Monday, the White House asked Congress for $1.8 billion in emergency spending to boost its coronavirus response.

“The administration believes additional federal resources are necessary to take steps to prepare for a potential worsening of the situation in the United States,” acting White House Office of Management and Budget director Russell Vought said in a letter to congressional leaders.

Separately, President Trump said Tuesday that the U.S. stock market would crash if he didn’t win reelection. Trump routinely cites the strength of the U.S. markets, which have long been trading at or near record highs, as a barometer of his presidency. From the White House to the campaign trail, he touts that success as one of his chief accomplishments.

Speaking at a business roundtable during his 36-hour visit to India, Trump said the markets will see a boost if he wins in November. But “if I don’t win, you’re going to see a crash like you’ve never seen before,” Trump said.

Jeffrey Stein contributed to this report.