NSW Health officials have pledged to leave "no rock unturned" as they hunt for any cases linked to a security guard at a Sydney quarantine hotel who tested positive to COVID-19.
But the state's chief health officer Kerry Chant played down fears of a Victorian-style quarantine breach at the Marriott Hotel in Circular Quay, saying: "I think it's important that we keep a perspective on this."
Genome sequencing has linked the guard's infection to a returned traveller who was in quarantine at the Marriott and tested positive on 2 August.
Dr Chant says the guard worked at Sydney's Flemington Markets and Parramatta Local Court while infectious.
The guard also worked at the Marriott on 3, 4, 7 and 8 August, but was not infectious at the time, and developed symptoms on 11 August.
"The exact nature of how that infection could have been acquired is a matter that's under intense investigation," Dr Chant said on Tuesday.
But Dr Chant said there was no indication the case was a quarantine breach, and the strain identified in the guard is different to the Crossroads Hotel cluster and other outbreaks in Sydney that are linked to Melbourne.
"We haven't had evidence to date of other cases but, let me tell you we're not going to leave any rock unturned in terms of our search for confirming there are no further cases linked to (this) single case."
The security guard was one of 16 mystery cases recorded in NSW over the past four weeks that have been concerning health authorities.
It comes as the state recorded three new cases of coronavirus in the 24 hours to 8pm on Monday, the lowest daily number in more than a month.
They were diagnosed from 13,736 tests in the 24-hour period, compared with 10,806 tests and seven positive cases in the previous 24 hours.
On Wednesday, tougher COVID-19 restrictions will come into force at NSW public schools.
Formals, dances, graduation ceremonies, choirs and all social events have been banned and students must remain within their relevant class or year groups.
Schools must not travel outside their local community or zone and interschool sport and zone carnivals are restricted to 100 people per venue and held locally.
Spectators, including parents and carers, also won't be allowed on school grounds or at sporting events held during school hours.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.
