The United States topped three million confirmed coronavirus cases Wednesday as President Donald Trump pushed for schools to re-open amid a COVID-19 resurgence in many southern hotspots.

The US remains by far the worst affected country, with over 132,000 deaths, while Brazil -- whose virus-skeptic President Jair Bolsonaro has tested positive for the disease -- is a distant second with close to 67,000 deaths from almost 1.7 million cases.

Trump begins withdrawing his country from WHO
US President Donald Trump began withdrawing his country from the World Health Organization on Tuesday. Photo: AFP / Angela Weiss

As infections rose by a further 55,000 to reach a total of 3,046,351 on Wednesday, Trump called for students to return to their schools in the fall and lashed the Centers for Disease Control and Prevention for issuing guidance that he said was too restrictive.

The agency's head later said the guidelines were "not requirements" and that the CDC would soon update its advice.

Prestigious universities Harvard and MIT meanwhile sued the administration after it threatened to revoke the visas of foreign students whose entire courses have moved online because of the coronavirus pandemic.

Bolsonaro has played down effects of Covid-19
Jair Bolsonaro has consistently played down the effects of the disease, mocking it as a "little flu". Photo: AFP / MAURO PIMENTEL

The virus has infected almost 12 million people worldwide and killed more than 500,000 since it emerged in China late last year.

Belgrade protests
Dozens were hurt, police cars set alight and the parliament building breached in Belgrade's protests. Photo: AFP / Oliver BUNIC

Across the world, citizens chafed under renewed restrictions as countries experience fresh waves of disease.

The Serbian capital Belgrade was hit by clashes for a second night as police skirmished with protesters outraged over the government's handling of the pandemic.

Clouds of tear gas and smoke filled the city center in chaotic scenes that mirrored violence the night before, when thousands came out to protest the return of a round-the-clock weekend lockdown.

Australia seals of Victoria
Australia is sealing off the state of Victoria from the rest of the nation -- a move that has sparked panic-buying. Photo: AFP / William WEST

In the Australian city of Melbourne, millions were preparing for a return to lockdown to fight an upsurge that is seeing more than 100 new cases reported each day, with panic buyers stripping supermarket shelves.

France, which had flattened its curve by imposing a strict lockdown earlier in the pandemic, said Wednesday it was girding for a possible surge in cases.

COVID-19 worldwide
New COVID-19 cases per day by world region since February 2. Photo: AFP / Cléa PÉCULIER

But, mindful of potentially disastrous consequences of attempting to thrust millions back into their homes, France's new prime minister aimed to soothe fears by promising no new full shutdown.

"We're not going to impose a lockdown like the one we did last March, because we've learned... that the economic and human consequences from a total lockdown are disastrous," Jean Castex said, promising "targeted" measures instead.

Alberto Gomez's botanical garden
Everyday Alberto Gomez tends to his Botanical Garden, which he founded over 40 years ago in Colombia, the second most biodiverse country in the world. But the pandemic forced him to close its door to the public, and he quarantined there alone, among the plants and butterflies. Photo: AFPTV / Freddy NAVARRO

Several US states and cities have likewise had to roll back their reopening measures. Houston, for example, on Wednesday canceled the Texas Republican Party's upcoming in-person indoors state convention as COVID-19 cases surged in the city.

Having just a handful of cases at the start of February, the US infection rate passed the one million milestone on April 28 and hit two million on June 11, according to an AFP tally of official sources.

All the while, the death toll has been creeping up to its current figure of more than 132,000, almost one-quarter of the global total.

The current US death rate is however substantially lower than it was in late spring.

This is possibly because of a lag between infection and deaths among sick patients, but also because the country's epidemic is affecting younger people, and because better treatments are now available.

Doctors have found that placing patients with breathing troubles on their stomachs eases the burden on their lungs, and are using blood thinners preventatively to stop catastrophic clots from forming as a result of the virus.

They are also using the steroid dexamethasone to stop a supercharged and destructive immune response, and the antiviral remdesivir to help ventilated patients recover faster.

Trump, for his part, has sought to blame China and the World Health Organization for his country's epidemic, and on Tuesday formally began the process of withdrawing from the body.

His opponent in the November election, former Vice President Joe Biden, has vowed to undo the decision if he wins.

The virus continues to take a massive economic toll, sparking an explosion in Canada's federal budget deficit, which hit CAN $343 billion (US $254 billion) for the current fiscal year.

The European Union meanwhile is working on a $843 million package to help crisis-hit economies in the bloc.

"We need extraordinary solidarity," said German chancellor Angela Merkel ahead of an upcoming EU summit.

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