New South Wales health officials have said they know how a Sydney man became infected with Covid-19 after his wife tested positive to the virus today.
NSW Premier Gladys Berejiklian said "health detectives" had managed to trace the source of the man's infection.
Genome analysis revealed the likely source was a person who arrived from the US and attended special health accomodation after testing positive upon arrival in Australia.
But it's still not clear how the virus managed to spread from that person to the man, who lives in the eastern suburbs of Sydney, who was confirmed positive on Wednesday.
"We can't find any direct link between our [cases]," NSW chief health officer Kerry Chant said.
"So what we're concerned about is that there is another person that is yet to be identified that infected our case."
Chant said the health department believed the virus strain originated in India. However, it was not currently considered a "variant of concern", the term the department uses for certain highly transmissible versions of the coronavirus such as those that originated in the UK and South Africa.
The man visited a number of venues in Sydney before he realised he was infected, including a CBD restaurant where NSW Treasurer Dominic Perrottet was having coffee at the same time.
Perrottet has since tested negative for the virus but will remain in self-isolation for 14 days starting last Friday.
The fears of continued community spread prompted Berejiklian to announce a raft of new restrictions for greater Sydney.
Residents will be required to adhere to the following public health guidelines from 5pm on Thursday until 12am on Monday:
• No more than 20 people allowed inside a home.
• No singing or dancing in indoor venues, including places of worship and entertainment venues – the exception is weddings.
• Masks will be compulsory at all indoor venues.
• Only two visitors allowed per resident in aged care facilities.
Berejiklian said the measures would only apply to people in the greater Sydney area – from Central Coast, greater Sydney down to Illawarra.