In just weeks, top economists and investment bank analysts have gone from expecting the coronavirus to have minimal impact on the U.S. economy to warning that an outright recession may be on the horizon, Axios Markets Editor Dion Rabouin writes.

• The spread of confirmed cases in Europe, the Middle East and the U.S., and the speed at which they are being discovered, has set the table for the outbreak to have a larger and much costlier impact.
• The outbreak threatens consumer-oriented businesses — restaurants, bars, travel. They had held up the U.S. economy as business investment fell and manufacturing dropped into recession, largely because of the U.S.-China trade war.
• Europe and Japan are particularly at risk: Both have generated only 1% growth over the past year and are very susceptible to falling into recession.

Flashback: Just a few weeks ago, many economists thought the coronavirus would cause only a tenth of a percentage point decrease in U.S. growth this year.

• But the S&P 500 has fallen by 10% in just six trading sessions, the fastest correction in history from a record high, Deutsche Bank Securities chief economist Torsten Sløk said in a note to clients.

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Spending on the 2020 presidential primary has officially surpassed the $1 billion mark, with more than half of that total coming from Mike Bloomberg, Sara Fischer writes from Advertising Analytics data.

• Why it matters: That's the most that has been spent this early in an election cycle in U.S. history.

For context, experts project that more than $10 billion will be spent on political ads this election season, with more than $3 billion toward the presidential primary specifically.

• In other words, roughly one-third of the total money that will be spent on presidential political ads has already been spent with eight months to go until Election Day.

By the numbers: Democrats have outspent Republicans more than 9-to-1 due to a highly competitive primary contest and because there are two billionaires spending an unprecedented amount on ads.

• So far, Democrats have spent a whopping $969 million on ads, compared with $67.9 million by Republicans.
• Bloomberg has spent more than $538 million to date, per Ad Analytics, while fellow billionaire Tom Steyer has spent more than $186 million.
• All other candidates have spent less than $50 million each.

Startling stat: One of the biggest shifts between 2016 and 2020 has been the increase in money invested in Super Tuesday states — mostly as a result of Bloomberg's unorthodox campaign strategy.

• About $247 million has been spent in Super Tuesday states, up from only $30 million in 2016.

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Schools across the U.S. are canceling trips abroad, preparing online lessons and even rethinking "perfect attendance" awards as they brace for the possibility that the coronavirus spreads to their communities, AP's Collin Binkley reports.

• If schools are forced to close for long stretches, it could have a heavy impact on students who rely on school meals and for parents who use their schools' child care programs.

Cleaning crews have been told to pay extra attention to door knobs, keyboards and other surfaces that students touch through the day.

• Some districts have invested in handheld disinfectant sprayers that are used in hospitals.
• Others are adding hand sanitizers in schools and buses.

Officials are considering how they would handle large numbers of absences among students or teachers, and how to make up days that could be missed because of the virus.

• In Miami, public school leaders said they're readying 200,000 laptops and tablets for students in case buildings close and force classes online.

The National School Boards Association is asking districts to reconsider attendance awards to students who don't miss a day of class for an entire year or semester.

• Some schools have previously abandoned the practice amid fears that it encourages students to come to school sick, but some still award gift cards, cash or raffle prizes to students with perfect attendance.

Syria's campaign to retake the final rebel strongholds in Idlib Province — backed by Russian strikes on schools, hospitals and homes — has displaced 1 million people and counting, Axios World Editor Dave Lawler reports.

• Many in Idlib are sleeping in cars, in caves, in sports stadiums or on the street in bitter winter weather.
• About half are children.

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From London, here's how The Economist sees the prospect of a Trump v. Sanders general election in the former colonies:

Sometimes people wake from a bad dream only to discover that they are still asleep and that the nightmare goes on.

Keep reading.

The Iowa Democratic Party released updated results of the Iowa caucuses after the completion of a recount requested by Bernie Sanders and Pete Buttigieg:

• Buttigieg has 562.954 state delegate equivalents and Sanders has 562.021 state delegate equivalents out of 2,151 counted.
• That is a margin of 0.04 percentage points.

AP says it won't call a winner, given irregularities that undermined the count.

• The party plans to certify the results tomorrow. At that point, the caucuses will formally end, and no further changes to the results will be made.

The Dow industrials had their worst-ever daily points drop — 1,191 — and the S&P 500 posted its largest percentage drop since August 2011.

• Oil prices tumbled to their lowest in over a year. (Reuters)

The latest: Stock indexes around the world today followed Wall Street into correction territory. (Wall Street Journal)

• CNBC headlines: "STOCKS ON TRACK FOR WORST WEEK SINCE FINANCIAL CRISIS ... DOW DROPS 3,200+ THIS WEEK."

Coronavirus disruptions, told in headlines:

• "Swiss government bans all events over 1,000 people"
• "New virus prompts Mormons to cancel key leadership event"
• Facebook cancels F8, its annual conference for developers
• "National Symphony cancels Japan concerts"
• "Serie A's biggest match will be played in empty stadium"
• "Saudis close Islam's holiest sites to foreigners"
• "South Korea, US postpone annual military drills"
• "Virus fears lead K-pop superstars BTS to cancel Seoul shows"
• "Tokyo Disneyland to close through mid-March"

"As soon as next month, Walmart plans to start publicly testing a membership program called Walmart+," Recode's Jason Del Rey scoops.

• "The program is expected to essentially launch as a rebrand of Walmart’s existing Delivery Unlimited service, which charges customers $98 a year for unlimited, same-day delivery of fresh groceries."

The paid membership program "would include perks that Amazon can’t replicate, in part to avoid a direct comparison to Prime."

• Walmart+ ultimately "could include discounts on prescription drugs at Walmart pharmacies and fuel at Walmart gas stations, as well as a Scan & Go service that would allow shoppers to check out ... without waiting in line."

This NASA image shows the Ophiuchus galaxy cluster, viewed in a composite of X-ray, radio and infrared data.

• Astronomers have discovered the biggest explosion seen in the universe, AP reports.
• Scientists reported that the blast, which was first detected in 2016 and appears to be over by now, came from a black hole in a cluster of galaxies 390 million light-years away.