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

Almost two years after the first cases were reported, 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.

The average number of daily COVID-19 cases in the US 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.

Many countries are still ­grappling with the earlier ­Delta variant, including Poland, which reported 794 virus-­related deaths on Wednesday - the highest number in the fourth wave of the pandemic.

Deputy Health Minister Waldemar Kraska said more than 75 percent of those who died were unvaccinated.

Early data from Britain, South Africa and Denmark suggests there is a reduced risk of hospitalization for the Omicron compared with the Delta variant, the World Health Organization said in its latest epidemiological report released overnight.