NSW Premier Dominic Perrottet has warned the COVID-19 pandemic is not over, as urgent genomic sequencing is undertaken to establish if the highly mutated Omicron strain has already reached Sydney.

Two people who arrived in the state from Africa overnight tested positive to the virus on arrival, with authorities expected to know by Sunday evening whether they have the Omicron B.1.1.529 variant of concern.

Some 29 people who’d been in one of the nine southern African countries subject to elevated restrictions touched down in Sydney across two flights on Saturday evening.

They’ve all been placed in hotel quarantine.

The two positive cases were on the same Qatar Airways flight from Doha that flew in at 7pm.

All passengers must isolate

All passengers on the flight are now classified as close contacts and must isolate for 14 days, even if they haven’t been in southern Africa.

Premier Dominic Perrottet says it’s a reminder that the pandemic is not over, and described his approach as precautionary.

However, he cautioned that it must be expected that the variant will spread throughout the world.

“We need to learn to live alongside the virus. We need to learn to live alongside the variants of the virus,” he said.

Although he’s ordered all international arrivals to quarantine at home for 72 hours, Mr Perrottet insisted the NSW international and state borders would remain open.

“We can’t be a hermit kingdom on the other side of the world,” he said.

“There’s only so much governments can do. The best thing we can do as a people is to get vaccinated, get a booster shot, and that will keep you and your family safe.”

The three-day quarantine order is on top of a federal government requirement for travellers to enter quarantine for two weeks if they’ve been in South Africa, Lesotho, Botswana, Zimbabwe, Mozambique, Namibia, Eswatini, Malawi or the Seychelles within the past 14 days.

Roadmap remains unchanged

There are no plans to adjust the state’s reopening roadmap, Mr Perrottet said, so restrictions will still ease for the unvaccinated on December 15.

The COVID and economic recovery committee, formerly known as crisis cabinet, will meet on Sunday afternoon to discuss the threat.

Health Minister Brad Hazzard said not much is known about the new strain, though it may be more transmissible than Delta. In particular, the effectiveness of current vaccines against Omicron is still being established, he said.

Mr Hazzard said it only took the Delta variant three weeks to reach 53 nations.

“We have to expect that Omicron may well … already be here,” he said.

Anyone already in NSW who has been in the nine southern African countries within the previous 14 days must immediately be tested, isolate for 14 days and contact NSW Health.

Meanwhile, the state added 185 new infections to its caseload on Sunday.

For the fourth day in a row, no new deaths were reported.

NSW hospitals continue to treat 165 patients, nine fewer than the previous day. Twenty-four are in intensive care units, 21 of whom are unvaccinated, and nine are ventilated.

Testers processed more than 54,000 results in the 24 hours to 8pm on Saturday.

NSW is 94.5 per cent single-dosed for everyone 16 and over, while 92.4 per cent are fully vaccinated.

Of 12- to 15-year-olds, 81.3 per cent have received one jab and 76.5 per cent both.

-AAP