Coronavirus: What's happening in Canada and around the world on Wednesday

The latest:

Daily COVID-19 infections have hit record highs in the United States, swathes of Europe and Australia as the new Omicron variant of the virus races out of control, keeping workers at home and overwhelming testing centres.

Almost two years after China first reported a cluster of "viral pneumonia" cases in the city of Wuhan, the regularly mutating coronavirus is wreaking havoc in many parts of the world, forcing governments to rethink quarantine and test rules.

Although some studies have suggested the Omicron variant is less deadly than some of its predecessors, the huge numbers of people testing positive mean that hospitals in some countries might soon be overwhelmed, while businesses might struggle to carry on operating because of workers having to quarantine.

France, Britain, Italy, Spain, Portugal, Greece and Malta all registered a record number of new cases on Tuesday.

Several Canadian provinces — including Quebec, Manitoba and two Atlantic provinces — saw single-day COVID-19 case highs on Tuesday, as health officials across the country struggled with strains on testing and tracing systems.

The average number of daily COVID-19 cases in the United States has also hit a record high over the past seven days, according to a Reuters tally. The previous peak was in January of this year.

New daily infections in Australia spiked to nearly 18,300 on Wednesday, eclipsing the previous pandemic high of around 11,300 hit a day earlier.

Australian Prime Minister Scott Morrison said his country needed "a gear change" to manage overburdened laboratories, with long walk-in and drive-in queues reported in a number of areas.

Testing bottlenecks have also built in European nations, including Spain, where demand for free COVID-19 testing kits provided by Madrid's regional government far outstripped supply on Tuesday, with long queues forming outside pharmacies.

A number of governments were also increasingly worried by the huge numbers of people being forced into self-isolation because they had been in contact with a coronavirus sufferer.

"We just can't have everybody just being taken out of circulation because they just happen to be at a particular place at a particular time," Australia's Morrison told reporters.

Italy was expected to relax some of its quarantine rules on Wednesday over fears the country will soon grind to a halt given how many people are having to self-isolate protectively, with cases doubling on Tuesday from a day earlier to 78,313.

However, China showed no letup in its policy of zero tolerance to outbreaks, keeping 13 million people in the city of Xi'an under rigid lockdown for a seventh day as new COVID-19 infections persisted, with 151 cases reported on Tuesday.