Nations in Asia imposed new restrictions on Monday and an abrupt British quarantine on travellers from Spain threw Europe's vaunted summer reopening into disarray, as the world confronted the prospect of a second wave of COVID-19 infections.
In the United States, where infection rates have climbed since June, President Donald Trump's national security adviser Robert O'Brien became the most senior official to test positive. The White House said Trump and Vice President Mike Pence were not at risk.
Surges were reported in a number of countries previously singled out as places where the virus was under control.
Australia recorded a record daily rise. Vietnam locked down the city of Danang, forcing tens of thousands of visitors to evacuate. Mainland China confirmed the most locally transmitted cases since early March. Papua New Guinea shut its borders.
Hong Kong banned gatherings of more than two people, closed down restaurant dining and introduced mandatory face masks in public places, including outdoors.
Just weeks after European countries trumpeted the reopening of tourism, a surge in infections in Spain prompted Britain to order all travellers from there to quarantine for two weeks, wrecking the travel plans of hundreds of thousands of people.
The World Health Organization said travel restrictions could not be the answer for the long term, and countries had to do more to halt the spread by adopting proven strategies such as social distancing and wearing masks.
"It is going to be almost impossible for individual countries to keep their borders shut for the foreseeable future. Economies have to open up, people have to work, trade has to resume," WHO emergencies programme director Mike Ryan said.
"What is clear is pressure on the virus pushes the numbers down. Release that pressure and cases creep back up."
"SPAIN IS SAFE"
Officials in some of the European and Asian countries where the virus is spreading again say new outbreaks will not be as bad as the original waves that hit earlier this year, and can be contained with local measures rather than nationwide shutdowns.
Spanish officials were stunned by Britain's sudden quarantine. Britain accounts for more than 20% of foreign visitors to Spain, where tourism represents 12% of the economy and reopening the industry was a major step towards recovery.
"Not only is it unjust but it's also totally illogical and lacking in rigour," Spain's main hotel association CEHAT said, as hotels offered to pay for coronavirus tests.
A British junior health minister said more European countries could end up on the red list after Spain: "If we see the rates going up, we would have to take action because we cannot take the risk of coronavirus being spread again across the UK," Helen Whately told Sky News.
Airlines and travel businesses that held on to survive the first wave now worry that an aborted reopening could be fatal.
Europe's biggest airline, Ryanair cut its annual passenger target by a quarter on Monday and warned a second wave of COVID-19 infections could lower that further.
Europe has yet to lift bans on travellers from many countries, including the United States, where Trump encouraged states in the spring to reopen quickly after a lockdown, and many are now setting infection records.
A pandemic-shortened baseball season, launched last week in front of empty seats, suddenly appeared in jeopardy after the Miami Marlins announced they had cancelled their first home game. Twelve players and two coaches tested positive while on the road in Philadelphia.
Emergency US federal unemployment benefits enacted in response to the pandemic expire this week. Republicans in Congress were expected to unveil a proposal on Monday to extend them at a reduced rate, setting the stage for a showdown with Democrats seeking a more generous stimulus bill.
In China, which managed to squelch local transmission through firm lockdowns after the virus first emerged in the central city of Wuhan late last year, a new surge has been driven by infections in the far western region of Xinjiang.
In the northeast, Liaoning province reported a fifth straight day of new infections and Jilin province reported two new cases, its first since late May.
Australian authorities who have imposed a six-week lockdown in parts of the southeastern state of Victoria said it could last longer after the country's highest daily increase in infections.
In Japan, the government said it would urge business leaders to ramp up anti-virus measures such as staggered shifts, and aimed to see rates of telecommuting return to levels achieved during an earlier state of emergency.
"At one point, commuter numbers were down by 70 to 80%, but now it's only about 30%," Economy Minister Yasutoshi Nishimura said. "We really don't want to backtrack on this."
Vietnam is evacuating 80,000 people, mostly local tourists, from Danang after three residents tested positive at the weekend. Until Saturday, the country had reported no community infections since April.
Papua New Guinea halted entry for travellers from Monday, except those arriving by air, as it tightens curbs against infections that have more than doubled over the past week.