Global markets soared Wednesday on reports of a breakthrough treatment for the coronavirus — despite a skepticism from public health officials — as investors saw cause for optimism that the deadly outbreak could be stopped before inflicting deeper economic wounds.

The Dow Jones industrial average was up 483 points at the day’s end, extending its rally a third day, while the Standard & Poor’s 500 swelled nearly 1.1 percent, closing at 3,334.69, a record. Tech-heavy Nasdaq advanced 0.43 percent on Wednesday. European markets have nearly erased the losses from last week’s panic about the outbreak that has sickened 24,000 people and killed nearly 500, with the benchmark Stoxx 600 index up 1.3 percent and approaching an all-time high. The Shanghai composite index continued to crawl back from its recent brutal sell-off, also closing up 1.3 percent.

A TV station in China reported that researchers at Zhejiang University had discovered an effective treatment for the virus, which has spread to more than 20 countries, according to officials. In Britain, researchers told Sky News a vaccine could be tested by next week.

“It seems, the world is nearing a cure for the coronavirus, and that could mean markets may only need to price in only one bad quarter of data for China,” Ed Moya, an analyst with Oanda, wrote in commentary Wednesday. “Financial markets may get overly optimistic on these early headlines, but the playbook remains once Wall Street is beyond the virus, risky assets will remain supported on central bank stimulus and the global growth rebound story.”

The World Health Organization, however, did not confirm the reports and issued a statement saying there are no known cures for the coronavirus. At a news conference Wednesday, the organization said it had seen more than 3,100 new cases in China alone and called for $675 million in funding to contain the virus.

Meanwhile, companies with household names are warning investors that the outbreak will have consequences for their bottom lines. Nike, which has closed half its stores in China, said the outbreak will have a “material impact” on its operations in the country. Disney has said it could take a $175 million hit in operating income if its theme parks in China are shuttered for the next two months. Apple, which has closed all its stores and offices in China and has suppliers in Wuhan, the center of the outbreak, gave investors an unusually wide revenue outlook range to account for the uncertainty this quarter. McDonald’s, Starbucks, KFC, Levi Strauss, H&M and Samsung have closed stores across China. Casinos in Macao, the world’s biggest gambling market, are shutting down for two weeks.

The airline industry, already embattled by Boeing’s ongoing trials, has been hit hard as carriers around the globe suspend services to China in the face of travel restrictions and vacant demand. Forty airlines around the world have cut or halted service to the country, and Boeing and Airbus announced Wednesday that they were halting production in Chinese factories. The auto industry has also been hammered, as General Motors, Toyota and Volkswagen suspended their Chinese operations.

U.S. markets were buoyed by an ADP and Moody’s Analytics report showing the biggest monthly gain in private payrolls since May 2015. Private payrolls added 291,000 jobs in January, nearly double what experts had predicted.

Oil staged a major recovery after prices fell to a one-year low earlier this week, with Brent crude trading up 2.8 percent at $55.46 a barrel Wednesday morning. The virus has all but halted travel in China, the world’s leading oil consumer, and prompted air carriers and tourism companies to announce widespread cancellations. BP has warned the virus could reduce global oil demand by as much as 80 percent this year. OPEC and its allies have been meeting to discuss oil output in the face of declining demand.

“While we do not yet know the severity of the coronavirus outbreak, which is still largely contained within China, a substantial increase in its scope globally would have significant negative implications for the energy market,” analysts at Moody’s wrote in commentary Wednesday. “Past virus outbreaks did not hurt oil and gas demand as much, and while investors should be cautious, whether this time is different still remains to be seen.”

Experts have been using the 2003 SARS (severe acute respiratory syndrome) outbreak to gauge the potential fallout from the coronavirus on global growth, and a 2004 study from the Brookings Institution, Korea University and the Australian National University estimated the outbreak delivered a $40 billion blow to the global economy; that would amount to about $56 billion today, adjusting for inflation. But the stakes are far higher now, as China is now one of the world’s most vital economic engines: Its gross domestic product is roughly $13 trillion, compared with its $1.6 trillion GDP during the SARS outbreak.

Even if the current outbreak is contained soon, economists predict China’s growth rate will drop to between 3 and 4 percent this quarter.

At a Bipartisan Policy Center event Tuesday, former Federal Reserve chair Janet L. Yellen said that though past epidemics such as SARS delivered a short-term economic blow, it is unclear whether that will be the case with the coronavirus.

“China is such a significant piece of the global economy that it’s bound to have spillover effects,” she said.

The outbreak has come at a pivotal moment, when the global economy was expected to rebound thanks to the trade truce between the United States and China. Fresh data from the Commerce Department on Wednesday showed that the U.S. trade deficit with China narrowed in 2019 for the first time in three years, as both nations slapped tariffs on hundreds of billions of dollars worth of imports. The deficit with China fell $73.9 billion to $345.6 billion last year.

The virus has brought China’s powerful manufacturing industry to a standstill, as most factories throughout the country have been idled until mid-February while travel restrictions have the Chinese workforce in a veritable lockdown.

Tesla, whose shares have more than doubled this year, saw its stock crater more than 17 percent Wednesday after announcing it will delay highly anticipated Model 3 deliveries due to Chinese factory closures. Tesla’s stock is still up 80 percent for the year.

“China is the linchpin for the bull thesis in Tesla over the coming years,” Dan Ives, an analyst with Wedbush Securities, said in commentary Wednesday. “The news this morning will certainly ruffle the feathers of the China Tesla thesis bulls, however we believe it represents a speed bump that will be short lived and could move out a handful of deliveries in the region from March to the June quarter.”