In less than three months, the novel coronavirus has spread from an unknown pathogen located in a single Chinese city to a global phenomenon that is affecting nearly every part of society.

U.S. stocks closed more than 7% lower on Monday, after a wild day that saw a rare halt in trading, Axios' Courtenay Brown reports.

• Why it matters: The sell-off reflects serious fears that the coronavirus could help drive the economy into a recession.

Italy's prime minister announced that the government has extended internal travel restrictions to the entire country until April 3 and that all public gatherings and sporting events would be banned.

• Why it matters: It's an extreme measure that effectively locks down 60 million people in one of the most populated countries in Europe, where more people have tested positive for the coronavirus than in any country outside of China.

Hospitals are reporting that their supplies of critical respirator masks are quickly dwindling, the New York Times reports.

• Why it matters: Keeping health care workers healthy will be critical as hospitals and other facilities see a surge in patients as the coronavirus spreads.

President Trump said yesterday that he will be meeting with Senate Republican leaders today to discuss a "very substantial" payroll tax cut and relief for hourly workers in order to stem economic damage from the coronavirus outbreak.

Federal regulators are cracking down on scams advertising unproven coronavirus treatments, and those frauds are likely to continue, Axios' Bob Herman and Marisa Fernandez report.

The big picture: Disease outbreaks have long created fertile ground for fraudsters to prey on the public's fears with fake or unproven treatments. COVID-19 is no different.

Driving the news: The Food and Drug Administration and the Federal Trade Commission issued warning letters yesterday about seven fraudulent products.

• Major retailers and some online marketplaces have already removed more than three dozen listings — for products including teas, essential oils, tinctures and colloidal silver — that falsely claim to help treat or prevent coronavirus infection.

Flashback: Scammers have run this con before.

• Zika: Wristbands, patches and stickers falsely claimed they could propel the mosquito-borne virus.
• Ebola: Before there was a vaccine, the FDA warned against online pitches that marketed snake venom, vitamin C, nanosilver and herbs as cures.
• SARS: Promotions for air purifiers, cleaning supplies and even prevention kits were pulled off several websites in 2003.

Reality check: No drugs have been approved to treat this strain of the coronavirus.

• Society is, at best, 12–18 months away from finding out the effectiveness of any kind of vaccine or antiviral medication.

The bottom line: Listen to public health experts and doctors about how best to avoid the virus and, if necessary, how to treat it. Anybody trying to sell you a remedy over social media is most likely just trying to pick your pocket.

The threat of a pandemic has "become very real" but can "still be contained," the World Health Organization said Monday.

What we know, via Axios' Eileen Drage O'Reilly:

• Symptoms: People with COVID-19 tend to have a fever, a dry cough and shortness of breath. 80% have mild/moderate symptoms including mild pneumonia, per WHO.
• Complications: Per Bloomberg, there's a "tipping point" when the virus travels to the lower respiratory tract where complications become severe.

• Age matters: The mortality rate increases for those 60 and older. Over 80 years old, the mortality rate reaches above 21%, WHO said Monday.
• Health matters: WHO said Monday that initial data indicates the mortality rate for people with cardiovascular disease is 13%, diabetes 9%, chronic respiratory disease 8%, and cancer 5%.

What we still don't know:

• Fatality rate: As the National Institutes of Health's Anthony Fauci told Axios last month, it's impossible to determine this when "both the denominator and numerator [of cases] are unknown."
• Contagiousness: One person is likely to infect about two to three people. But we don't know why children appear to be protected, nor do we know how many people are asymptomatic and unreported.

Go deeper: The unknowns of the coronavirus nearing a pandemic

The coronavirus is already the most serious threat to the U.S. economy since the financial crisis, and the dominoes are aligned for a severe recession that could erase much of the 11-year recovery, Axios' Dion Rabouin and Dan Primack report.

What's happening: While the outbreak itself is unlikely to drive an economic collapse, the U.S. has been something of a ticking time bomb for some time.

• Growth has declined over the last two years despite higher government spending and a $23.4 trillion national debt.
• While the labor market has boomed, many of the jobs added have been hourly service-industry positions that offer limited scope for savings or health insurance.
• 44% of all U.S. workers earn barely enough to live on, a Brookings Institute study found in January.

One big difference between 2020 and 2008 is breadth. The financial crisis began with financial services companies and insurers, which meant bailouts and structural fixes could be aimed at Wall Street. But this crisis is hitting the entire economy with a single blow — harming not just the Fortune 500, but also mom-and-pop businesses.

Between the lines: The cavalry may not be coming to the rescue this time.

• The Federal Reserve, which helped rescue the economy after the 2008 crisis, is effectively out of ammunition.
• Government also increasingly looks broken. The dysfunction in Washington is dimming hopes for a major fiscal stimulus that economists say will be needed to offset the outbreak's negative impact.

The Trump administration finalized a rule yesterday that would make it easier for patients to share their health data with apps, hospitals and doctors, WSJ reports.

Between the lines: The rule is likely to benefit the growing health data industry, which uses the information to develop health care services. But opponents of the rule argue that it could also create data privacy issues.

What they're saying: Tech companies like Apple, Google and Microsoft — which are all trying to move into the health care space — have generally supported the rule, as have consumer groups that argue it's too difficult for patients to access and share their own health data.

The other side: “There is a legitimate concern that people will be sharing their sensitive health information with organizations that can use and sell that information however they want,” Joy Pritts, a consultant who is a former federal health-privacy official, told WSJ.

What we're watching: The American Hospital Association — which said in a statement yesterday that the rule "fails to protect consumers’ most sensitive information about their personal health" — didn't rule out litigation.

• “We are working our way through the hundreds of pages of the rule to better understand all the operational implications for our hospitals. We will then pursue changes through the relevant government agencies and channels," AHA senior vice president Ashley Thompson told Bob.

Aon is proposing to buy Willis Towers Watson in an all-stock transaction that would combine the second- and third-largest insurance brokerages, Bob writes.

Why it matters: Employers hire Aon and Willis Towers Watson to help them choose health plans and pharmacy benefit managers for their workers, but the major consultants don’t always steer companies toward the best deals.

• Combining into the largest consulting house on Earth will give Aon that much more power over employers.

What’s next: The two companies don’t expect to close the deal until the first half of 2021, indicating they know antitrust regulators will be closely scrutinizing this.

Go deeper: The unclear drug price coalitions between consultants and PBMs