BANGKOK (AP) — People around the world became increasingly closed off from one another Thursday as sweeping travel bans accelerated, walling regions apart as a viral pandemic unfolds and financial markets plunge.

It was an outbreak moving, at once, both glacially and explosively, with a virus first detected three months ago in China creeping across borders and producing eruptive outbreaks that have crippled areas.

Even for a crisis that has brought no shortage of headlines, dizzying developments were flashing across screens: An official designation of "pandemic" from the World Health Organization, a dramatic halt to much travel between the United States and 26 European countries, and infections among beloved Hollywood stars, sports luminaries and political leaders. All of it came against a backdrop of plunging world economies that left not only Wall Street investors but people from all walks of life hurting.

"We will see more cases and things will get worse than they are right now," said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases.

President Donald Trump, who had downplayed the virus for days, suddenly struck a different tone, delivering a somber Oval Office address announcing strict rules on travel from much of Europe to begin this weekend. The State Department followed with an extraordinary warning to Americans to "reconsider travel abroad" too. Local leaders warned things would only get worse.

"This will be a very difficult time," said Dr. Jeff Duchin a top public health official for the Seattle area, which has one of the biggest U.S. outbreaks. "It's similar to what you might think of as an infectious disease equivalent of a major earthquake that's going to shake us for weeks and weeks."

Across the U.S., where cases now number more than 1,300, a sense of urgency was pervasive.

Nursing homes turned away visitors, schools emptied of students and workplace cubicles went vacant. A rite of spring, college basketball's March Madness, was set to proceed in empty arenas, while professional basketball won't play at all. Joyous, booze-filled, green-splashed celebrations of St. Patrick's Day were called off. TV shows taped without audiences, rush-hour crowds in New York subway cars disappeared, and families hunkered down wondering what would come next.

"If we avoid each other and listen to the scientists, maybe in a few weeks it will be better," said Koloud 'Kay' Tarapolsi of Redmond, Washington, who has two children whose schools were being closed beginning Thursday.

As the pandemic grips Europe and the U.S., it continues to ebb in China, where the first cases of COVID-19 emerged in December. It reported a record low of just 15 new cases Thursday and was cautiously monitoring new arrivals who were returning with the virus from elsewhere.

More than three-fourths of China's patients have recovered. Most people have only mild or moderate symptoms, such as fever and cough, though symptoms can be severe, including pneumonia, especially in older adults and people with existing health problems. Recovery for mild cases takes about two weeks, while more severe illness may take three to six weeks, WHO says.

More than 126,000 people in more than 110 countries have been infected. But WHO emphasized the vast majority are in just four countries: China and South Korea — where new cases are declining — and Iran and Italy, where they are not.

"We have called every day for countries to take urgent and aggressive action," said WHO's leader, Tedros Adhanom Ghebreyesus. "We have rung the alarm bell loud and clear."

High-profile announcements of infections made the alarms even louder. Double Oscar winner Tom Hanks said he and his wife Rita Wilson tested positive. Australian officials say the couple are in a Queensland hospital and their close contacts would have to self-quarantine.

In Italy, soccer club Juventus said defender Daniele Rugani tested positive. In Iran, the senior vice president and two other Cabinet ministers were reported to have been diagnosed with COVID-19.

Italy, already under unprecedented restrictions, tightened rules even more. Italian Premier Giuseppe Conte announcing the closure of pubs, restaurants, hair salons, cafeterias and other businesses that can't ensure a meter (yard) of space between workers and customers.

"In this moment, all the world is looking at us," Conte said, as the rules brought an eerie hush to places around Italy.

Asian shares plunged Thursday, following a drop of 1,464 points of the Dow Jones Industrial Average, putting the index 20% below its record set last month and into fearsome territory Wall Street calls a "bear market."

"There's a real feeling that we don't know where this ends," said Brad McMillan, chief investment officer for Commonwealth Financial Network.

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Keaten reported from Geneva. Contributing to this report were Associated Press writers Maria Cheng in London; John Leicester in Paris; Colleen Barry in Soave, Italy; Nicole Winfield and Frances D'Emilio in Rome; Rachel La Corte in Olympia, Washington; Chris Grygiel and Lisa Baumann in Seattle; and Adam Geller, David B. Caruso and Theo Wayt in New York.

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The Associated Press receives support for health and science coverage from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.

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Follow AP coverage of the virus outbreak at https://apnews.com/VirusOutbreak and https://apnews.com/UnderstandingtheOutbreak