NSW health authorities are still working to trace the source of a 17-strong coronavirus cluster developing at an independent Catholic school in northwest Sydney.
At least six new COVID-19 cases were linked on Tuesday to Tangara School for Girls in Cherrybrook, following the previous identification of 11 cases.
After new case numbers last week began a slow downward trend, NSW recorded 22 new COVID-19 cases in the 24 hours to 8pm on Monday - four of which are in hotel quarantine, another two are linked to Victoria and eight from the Tangara cluster. Two of those eight Tangara cases had been identified on Monday.
It's the highest daily increase of COVID-19 cases in NSW for almost four months with 17 locally acquired cases being the highest number in that category since the end of July.
The Opus Dei-associated Tangara School school has now closed its secondary campus until 24 August and its junior campus until at least Wednesday after its first COVID-19 case last week.
NSW Health on Tuesday said the source of the Tangara outbreak remained unclear and all secondary students and staff were in self-isolation and being tested.
In Pennant Hills, St Agatha's Catholic Church is undergoing deep cleaning after a parishioner who visited last Wednesday and Thursday tested positive to the virus, as is PharmaSave Pharmacy in Cherrybrook after an infected employee worked on Thursday.
In western Sydney, Bonnyrigg Heights Public School reopened on Tuesday after being closed for cleaning on Monday after a primary school student tested positive, but Kids' Early Learning Quakers Hill remains closed after children were exposed to the virus.
A second student at Our Lady of Mercy College in Parramatta has also caught COVID-19.
After three weeks with no new cases linked to the Batemans Bay Soldiers Club cluster, the local high school and Batemans Bay Public School on the NSW south coast are both closed on Tuesday after one student at each school tested positive for the virus.
They were both contacts of a confirmed case at the Batemans Bay Soldiers Club.
NSW Chief Health Officer Kerry Chant has urged people to avoid large gatherings and this week admitted older school students are more likely to transmit the virus.
"The older the students are, they behave more like adults," Dr Chant told reporters.
"We still know and believe younger students such as primary school students are not likely to be infecting (others) but as you get older ... an 18-year-old at school is more like an adult in terms of their characteristics, the risks of transmission."
Premier Gladys Berejiklian said the state remained on high alert and added that non-government schools such as Tangara should have already stopped extracurricular activities.
"We are in a pandemic - every organisation, every entity needs to abide by the COVID-safe plans," Ms Berejiklian told reporters on Tuesday.
"My anxiety has not subsided in relation to what a knife-edge NSW is on, but we need to keep pulling together and keep doing the right thing.
"I don't want people living with the guilt of passing on the disease or causing the spread because they could've prevented something from happening."
Eight COVID-19 patients in NSW are currently in intensive care, with six ventilated.
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.
