Mushrooming outbreaks of the Delta variant prompted China and Australia to impose stricter Covid-19 curbs on Saturday, as the WHO urged the world to contain the mutation before it turns into something deadlier and draws out the pandemic.
China's most serious surge of coronavirus infections in months spread to two more areas Saturday -- Fujian province and the megacity of Chongqing -- in an outbreak that now spans 14 provinces.
More than 200 cases have been linked to an original Delta cluster in Nanjing city where nine cleaners at an international airport tested positive.
"The main strain circulating at present is the Delta variant... which poses an even greater challenge to virus prevention and control work," said Mi Feng, spokesman for China's National Health Commission.
The nation where the disease first emerged has rushed to prevent the highly transmissible strain from taking root by putting more than one million people under lockdown and reinstituting mass testing campaigns.
Worldwide, coronavirus infections are once again on the upswing, with the World Health Organization announcing an 80 percent average increase over the past four weeks in five of the health agency's six regions, a jump largely fuelled by the Delta variant.
First detected in India, the strain has now reached 132 countries and territories.
"Delta is a warning: it's a warning that the virus is evolving but it is also a call to action that we need to move now before more dangerous variants emerge," the WHO's emergencies director Michael Ryan told a press conference.
Both high- and low-income countries are struggling to gain the upper hand against Delta, with the vastly unequal sprint for vaccines leaving room for variants to wreak havoc and further evolve.
In Australia, where only about 14 percent of the population is jabbed, the third-largest city of Brisbane and other parts of Queensland state entered a snap lockdown Saturday as a cluster of the Delta variant produced six new cases.
"The only way to beat the Delta strain is to move quickly, to be fast and to be strong," Queensland's Deputy Premier Steven Miles said while informing millions that they would be under three days of strict stay-at-home orders.
- 'Crippling the economy' -
Restrictions are also in place in many other parts of the Asia-Pacific region to combat Delta. In Malaysia a nationwide lockdown spurred protest Saturday as people defied the curbs to take to the streets, piling pressure on the country's embattled prime minister to resign.
Anger is growing at the government's handling of the virus led by Muhyiddin Yassin.
"This government is... crippling the economy and also destroying our country's democracy," Karmun Loh, taking part in the protest in downtown Kuala Lumpur, told AFP.
The Bangladesh government was easing curbs however despite a Delta surge, prompting hundreds of thousands of garment workers to rush back to major cities after the government said export factories could reopen from Sunday.
'The war has changed'
With the Delta variant spreading at speed, doubts are growing over the efficacy of vaccines against the strain.
The US Centers for Disease Control on Friday released an analysis that found fully immunised people with so-called breakthrough infections of the Delta variant can spread the disease as easily as unvaccinated people.
While the jabs remain effective against severe disease and death, the US government agency said in a leaked internal document that "the war has changed" as a result of Delta.
An analysis of a superspreading event in the northeastern state of Massachusetts found three-quarters of people sickened were vaccinated.
"As a vaccinated person, if you have one of these breakthrough infections, you may have mild symptoms, you may have no symptoms, but based on what we're seeing here you could be contagious to other people," Celine Gounder, an infectious diseases physician and professor at New York University, told AFP.
Asked if Americans should expect new recommendations from health authorities or new restrictive measures, US President Joe Biden responded, "in all probability", before leaving the White House by helicopter for the weekend.