It's likely a woman who has been circulating in Sydney and on the NSW Central Coast is the fifth person in NSW to have contracted the Omicron variant of COVID-19.
Initial testing strongly indicates one more overseas traveller, who arrived in Sydney on Thursday and is isolating at home on the Central Coast, has been infected with the Omicron variant, NSW Health said on Tuesday.
If confirmed, if will bring the total number of confirmed cases of Omicron in NSW to five.
The fully vaccinated woman in her 30s arrived in Sydney on flight QR908 from Doha before the 14 days compulsory quarantine was introduced for travellers from southern Africa, and travelled by private car to the Central Coast.
NSW Health is contacting all passengers and crew on her flight to advise them they are close contacts and will need to get tested and isolate for 14 days, regardless of their vaccination status.
NSW Health has listed numerous shops in Parramatta and Top Ryde, as well as shops and two fast-food outlets on the Central Coast, that were visited by the woman before travellers from southern Africa were directed to go into isolation.
Anyone who attended those venues at the times and dates listed is a casual contact and must immediately get tested and isolate until a negative result is received.
They should continue to monitor for symptoms and if any symptoms occur, get tested again.
NSW Health says initial testing on a second person who arrived on the same flight and is now in Broken Hill indicates they are unlikely to have been infected with the Omicron variant.
The person, who is fully vaccinated and asymptomatic, is isolating at home.
Health Minister Brad Hazzard said the woman "came in before the new arrangements ... so she has been out in the community and (NSW) Health is now investigating that".
"She has essentially been out in the Central Coast area," he told Seven News.
Two overseas travellers were diagnosed on Monday with the Omicron COVID-19 variant after they arrived in Sydney on Sunday from southern Africa on Singapore Airlines flight SQ211.
They are fully vaccinated and isolating in the Special Health Accommodation.
NSW Health is contacting all the passengers on that flight to advise they are close contacts and will need to get tested immediately and isolate for 14 days, regardless of their vaccination status.
Another international traveller, who is isolating at home in Sydney after arriving on a flight from southern Africa last Tuesday, has tested positive for the Delta variant.
This person also travelled to Melbourne on flight VA800, departing at 6am on Thursday and returned to Sydney on flight QF486, which left Melbourne at 7pm that evening.
Passengers in the surrounding seats on flight VA800 from Melbourne to Sydney have been deemed close contacts and all other passengers and air crew are casual contacts.
NSW recorded 179 new cases of COVID-19 and there were three COVID deaths recorded in the 24 hours until 8pm on Monday, ending a four-day run of zero deaths.
The latest COVID deaths include a western Sydney man in his 40s with underlying health conditions who died at Nepean Hospital.
A man in his 50s died at Tamworth Base Hospital and a woman in her 60s died at St Vincent's Hospital.
NSW Health said 62,166 tests were conducted in the past day.
Some 94.5 per cent of people aged 16 and older have had one dose of a COVID-19 vaccine, while 92.4 per cent are fully jabbed.
More than 81 per cent of teens aged 12-15 have had one dose of a vaccine, while 76.5 per cent of them have had two doses.
There are 160 people in hospital with COVID-19, 26 are in ICU and 11 are ventilated.
© AAP 2021