China has raised its emergency warning to its second-highest level and cancelled more than 60 per cent of the flights to Beijing amid .
It was a sharp pullback for the country that declared victory over COVID-19 in March and a message to the rest of the world about how tenacious the virus really is.
New infections spiked in India, Iran and the US as authorities struggled to balance restarting economic activity without accelerating the pandemic.
Officials of European countries, which embarked on a wide-scale reopening this week, looked on with trepidation as the Americas struggled to contain the first wave of the pandemic and Asian countries like China and South Korea reported new outbreaks.
Chinese officials described the situation in Beijing as "extremely grave".
"This has truly rung an alarm bell for us," Party Secretary Cai Qi told a meeting of Beijing's Communist Party Standing Committee.
After a push that began on June 14, the city expects to have tested 700,000 people by the end of the day, said Zhang Qiang, a Beijing party official.
About half of them were workers from the city's food markets, nearby residents and close contacts.
The party's Global Times said 1255 flights to and from the capital's two major airports were scrapped by Wednesday morning, about two-thirds of those scheduled.
Since the virus was detected in China late last year and spread worldwide, there have been more than 8.1 million confirmed cases and at least 443,000 deaths, according to a tally kept by Johns Hopkins University.
Experts say the true toll is much higher, due to the many who died without being tested and other factors.
The US has the most infections and deaths in the world, with a toll that neared 117,000 on Wednesday, surpassing the number of citizens who died in World War I.
Arizona reported a daily high of nearly 2400 new infections for a total of more than 39,000, while in Texas, Governor Greg Abbott insisted the state's health care system could handle the fast-rising number of new cases and hospitalisations.
Tuesday marked the eighth time in nine days that Texas set a new high for COVID-19 hospitalisations at 2518.
Mr Abbott noted that Texans may have become lax in wearing masks or practising social distancing and urged people to stay home as much as possible.
Canada and the US extended to 21 July a deal to keep their border closed to non-essential travel, with many Canadians fearing cases arriving from the US.
A healthcare worker checks the body temperature of a boy during a free coronavirus screening in Mumbai Source: SIPA USA
In South Korea, authorities reported 43 new cases amid increased public activity.
Authorities said 25 of them came from around Seoul, where hundreds of infections have been linked to nightclubs, church gatherings, e-commerce workers and door-to-door salespeople.
Twelve of the new cases came from international arrivals.
Not long after declaring itself virus-free, New Zealand detected a re-emergence of the virus.
Prime Minister Jacinda Ardern assigned a top military leader to oversee the border quarantines after what she described as an "unacceptable failure" by health officials.
Two New Zealand citizens who had returned from London to see a dying relative were allowed to leave quarantine before being tested.
After the women tested positive, New Zealand began tracing their potential contacts to ensure the virus is contained.
Their cases raised the spectre that international air travel could ignite a new surge of the virus just as countries seek to boost devastated tourism industries.
China also limited other travel around the capital, keying in on hot spots.
Beijing had essentially eradicated local transmissions until recent days, with 137 new cases since last week.
On Wednesday, the city of 20 million raised its threat level from 3 to 2, cancelling classes, suspending re-openings and strengthening requirements for social distancing.
India, with the fourth-highest caseload after the US, Brazil and Russia, added more than 2000 deaths to its tally after Delhi and Maharashtra states included 1672 previously unreported fatalities.
Its death toll of 11,903 is now eighth-highest in the world.
India has reported 10,000 new infections and more than 300 deaths each day for the last two weeks.
Iran's latest outbreak comes after a major Muslim holiday last month and as travel and lockdown restrictions were relaxed.
Health Minister Saeed Namaki said he realised the extent of the challenge when he took a domestic flight.
"Many people have become careless, frustrated with wearing masks," he said. "They did not observe (social) distancing in the flight's seating and the airliner's ventilation system was not working."
German officials said more than 400 people at a large meat-packing plant had tested positive for COVID-19, prompting authorities to order the closure of all schools and childcare centres in the western region of Guetersloh.
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