Post-Criminal and Civil War-era coronaviruses are circulating in Australia, the National Institute of Health has warned.
The first cases were detected in Sydney, Melbourne, Adelaide and Canberra on Sunday.
The Australian Centre for Disease Control and Prevention said it had received reports of people who have died or been hospitalised after coming into contact with the virus.
The number of reported cases has fallen from the peak of about 7,000 reported in the second week of October, to just under 3,000 in the third week.
The ABC’s 7:00 programme said the latest coronaviral infections in Australia could be as high as 8,000 cases.
It is unclear whether the latest cases are linked to the coronavaccine or the reintroduction of the vaccine, which was given to Australians aged 15 and over at the end of last year.
The vaccine, known as the quadrivalent vaccine, was developed to stop the spread of the coronajet, a strain of coronavillae that is believed to cause about 20 per cent of cases.
It is given to those aged 25 and over, as well as to those who are pregnant or plan to become pregnant.
The ABC understands the vaccine is still being tested in Australia.
If you are concerned about your health and want to talk to someone, call 111.