Of those 13, one is a returned traveller now in hotel quarantine, six are linked to the Sydney CBD cluster, two are close contacts of previously reported cases and four are locally acquired with their source still under investigation.

NSW Health data found that in almost half of the COVID cases in Sydney over the past week, people had waited several days after the onset of symptoms to get tested.

NSW Premier Gladys Berejiklian said this may be because people weren't treating their symptoms seriously.

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"We suspect it's because people are regarding an early onset of symptoms as nothing to worry about," Ms Berejiklian said.

"Given where we are in the pandemic, given the rate of flu is almost low or non-existent, if you have even the mildest of symptoms, don't assume it's the cold or the flu, you have to assume it's COVID.

"Every time you leave the house with a scratchy throat you have to assume it's COVID, so you need to get tested and stay home."

Deputy Commissioner Gary Warboys said ahead of the weekend that people need to understand quite clearly that public health orders are still in place.

The Deputy Commissioner said he expected complacency could set in, especially among people who have not had family or friends contract the virus.

"I see people thinking that everything is okay for them to move back to a very normal lifestyle," he said.

"I think that complacency is one of the things that will invariably see more infection, more disease and the whole community restricted in some way."