Genomic sequencing is under way to determine whether an international traveller who landed in Melbourne last week could have been infected with the new Omicron strain of COVID-19.

The traveller, who is fully vaccinated, arrived in Victoria from the Netherlands after transiting through Abu Dhabi on December 3 and went straight into hotel quarantine.

The person returned a negative PCR test on December 4 before developing symptoms and testing positive for the virus on December 6.

Health authorities said the test results had shown an S gene dropout in the virus, a sign a person could be infected with Omicron, according to the World Health Organisation.

“Several labs have indicated that for one widely used PCR test, one of the three target genes is not detected — called S gene dropout or S gene target failure– and this test can therefore be used as marker for this variant, pending sequencing confirmation,” the WHO said on November 26.

All other passengers on the inbound flight will be contacted to make sure they have been tested for the virus, as contact tracers try to determine the source of the infection.

The traveller has not been in the community while infectious. Overseas arrivals to Victoria need to quarantine for 72 hours upon arrival and undergo PCR testing within 24 hours. They have to get tested again between days 5 and 7.

Meanwhile, two elderly Aboriginal Victorians have died having tested positive for COVID-19, becoming the first Indigenous people in the state to die with the virus.

In a statement on Tuesday afternoon, health authorities confirmed a 68-year-old woman with coronavirus had died from an underlying health condition, while a 73-year-old man had died from COVID-19.