NSW residents have been urged to wear masks when they venture outside – although authorities have stopped short of making them mandatory, as they are in Victoria.

“If you are in the shopping centre, wear a mask. If you go on public transport, If you go to your place of worship, wear a mask. If you’re ever unsure, wear a mask,” Health Minister Brad Hazzard said on Wednesday.

“It’s not a matter of actually asking whether it’s OK to do it, it’s a case of just do it.”

Premier Gladys Berejiklian backed up the call later. She said she had worn a mask while buying groceries or at a shopping centre.

“If you’re in an environment where you can’t guarantee social distancing, you should be wearing a mask,” she said.

“We need to see a greater uptake. And if we don’t see a greater uptake in the next little while, we will consider further measures in which we can increase that uptake.”

Ms Berejiklian has also urged businesses, especially hospitality venues, to do more to meet virus measures – or they will also face tighter rules.

“If we don’t see greater compliance, we will need to take further action,” she said.

“We’ve given certainly a grace period for businesses, for organisations, for different establishments to step up their COVID safe plans – and if they don’t do that we will have to go a step further.”

NSW Health reported 18 more coronavirus infections on Wednesday, including two at a cluster connected to a private school in Sydney’s north.

“NSW continues to hold the line,” Ms Berejiklian said.

“But what concerns me, what concerns our experts is over the few weeks that we’ve been able to hold the line, there has been an accumulation of the number of cases which, as of today, do not have a direct link.”

The Tangara School for Girls outbreak has grown to 19, with NSW chief health officer Kerry Chant conceded tracing the outbreak was challenging.

Thirteen of NSW’s cases from Wednesday locally acquired and linked to known cases, one was a returned traveller from overseas, two were locally acquired without a known source and two were acquired in Victoria.

The source of the cluster from Tangara, in Cherrybrook, north-west Sydney, is yet to be pinpointed.

Dr Chant said it would be “challenging” to trace the origins of the Tangara outbreak.

NSW Health is investigating a retreat organised by the nearby Eremeran Hills Study Centre. The centre has said that five girls from years 10 and 11 had attended a retreat in Bargo, 100 kilometres south-west of Sydney.

The centre is now closed but none of its staff had tested positive.

“We are continuing to assist NSW Health in their endeavours to ascertain whether the retreat may have contributed to the outbreak,” the centre said in a statement.

A Tangara spokesman said the school did not know about the retreat and that no staff attended.

Meanwhile, two people infected with COVID-19 and linked to the Tangara outbreak also visited the Wildginger restaurant in Huskisson on the South Coast on Saturday, August 8.

The restaurant has been closed for a fortnight.

Dr Chant said it could take weeks to identify the source and “pieces of the puzzle” around the Tangara outbreak.

Other developments in NSW schools

• Parramatta Public School was closed on Wednesday for cleaning after a student tested positive to COVID-19;
• Nearby, Our Lady of Mercy College in Parramatta will be closed until August 24 after a third student tested positive this week. That case is not linked to the two earlier cases;
• Batemans Bay Public School and Bateman’s Bay High school were open again on Wednesday after students at both tested positive this week.

By Wednesday, there were 133 active COVID-19 cases in NSW, up from 113 on August 5.

There were eight virus patients in intensive care, seven on ventilators (compared to nine in ICU and six on ventilators on August 5).