So far, 24 people linked to The Argyle House nightclub exposure have tested positive for COVID-19.

While a "number" of these cases are "likely" to be the Omicron variant, NSW Health says, genomic sequencing is still underway.

All 680 people who checked in using the QR code to attend the venue from 9pm, on December 8, to 3am on December 9, have been assessed as close contacts and must immediately get tested and isolate for seven days.

COVID-19 case alerts also went out to people who attended the Great Northern Hotel on December 10 and 11.

NSW Health is appealing for anyone who did not check in using the QR code to urgently get tested and isolate, and for the community to ensure other potential attendees are aware of this advice.

"Given the high transmission of COVID-19 at the venue, we ask household contacts of anyone who attended to also immediately get tested and isolate until the close contact tests negative," NSW Health says.

"Everyone should remain vigilant when celebrating with family, friends and colleagues and should not attend any social functions if they have any symptoms."

There are more than 450 COVID-19 testing locations across NSW, many of which are open seven days a week. To find your nearest clinic visit COVID-19 clinics or contact your GP.