The state recorded 5715 cases on Thursday, just 10 shy of the nation’s total for Wednesday.

“As of midnight tonight, we will be requiring that masks are worn in indoor settings, ” NSW Premier Dominic Perrottet said.

Hospitality venues will move to a two-square metre rule from December 27, while QR codes will again be compulsory.

Acting Victorian Premier James Merlino also ordered masks for those aged eight and up in hospitality, entertainment and office settings from 11.59pm on Thursday.

Mr Perrottet said the move was “to ensure as we move through this period of time we do have that support for our health officers over this summer and holiday period.”

Since lifting most restrictions on December 15, the premier had struck a confident note and urged residents to take “personal responsibility” and help lead the nation out of the pandemic.

But cases have spiked since, with more than 20,000 testing positive since December 16 and testing clinics being overwhelmed.

In Victoria, masks will also be required at all major events with more than 30,000 patrons, including the Boxing Day Test at the MCG, but can be removed while seated outdoors.

They do not need to be worn in households.

Mr Merlino described the measures, which will remain until at least January 12, as modest.

“This is a sensible response which will allow businesses to stay open, bars and restaurants to continue to stay open and major events to go ahead,” he told reporters.

Only 52 per cent of cases were notified to NSW Health by laboratories within one day of sample collection in the week ending December 19, down from 85 per cent the previous week.

While 94 per cent of cases were fully interviewed by NSW Health within one day of notification the previous week, now only 54 per cent are.

The surge in cases has also seen the number of healthcare workers in isolation nearly triple – from 459 to 1364 – in a single week.

The dramatic spike in cases just two days before Christmas had already pushed the government to change its mind on mandatory check-ins to venues across the state.

Check-ins will be mandatory again at supermarkets, shops and hospitality venues.

Despite the rise in cases, health advice indicated disease caused by the Omicron variant appeared about five times less severe than Delta, Perrottet said.

Sydney remains the state’s epicentre of the virus, but transmission is also raging in the Hunter New England area, which has 976 new cases.

One death, an unvaccinated man in his 40s with underlying health conditions, was recorded on Thursday.

The number of people in hospital has climbed to 347, up 45, with 45 in ICU, 13 of whom are on ventilators.

Most of the intensive care patients are unvaccinated.