Bondi backpackers are among 97 more people to contract coronavirus in NSW.
NSW Health says there were two recent parties, which were attended by those who have contracted the virus.
"People who also attended these parties should be on alert for symptoms of COVID-19 and immediately isolate themselves if any symptoms develop," a spokesman said.
"They should then seek testing via a GP or COVID clinic, and tell the medical service that they had attended one of the parties."
The revelation comes a day after Bondi beach was closed because beach-goers were ignoring social distance requests.
The number of new cases in NSW rose by 97 in the 24 hours to 8pm on Saturday, March 21.
This compares with 83 in the previous 24-hour period and 75 the day before.
There have now been 533 confirmed cases in NSW.
NSW Health is urging people to practice social distancing.
"When social distancing actions are combined with good personal hygiene measures the spread of an epidemic through the community can be slowed," the spokesman said.
"This helps protect the most vulnerable members of the community.
"It also reduces the impact of the epidemic on essential, life-saving health services by reducing the size of the peak of the epidemic so health services can continue to provide high quality care to all patients.
"Everybody must play their part."