Barilaro isolating after parliament scare

John Barilaro on Thursday night said he was informed he was a close contact of a confirmed case that afternoon, and had since returned a negative test result.

He will be tested at least twice more, he said, before he is released from isolation at midnight on July 6.

"I will continue to perform my duties as Deputy Premier while isolating and adhering to all health advice," he said in a statement posted to Twitter.

NSW Health on Thursday warned anyone who visited parliament on Tuesday - state budget day - must monitor for symptoms and if they occur, get tested and isolate until they receive a negative result.

Anyone who visited the Strangers' Dining Room at parliament between 6pm and 9pm must immediately get tested and self-isolate until they receive further information from NSW Health.

Agriculture Minister Adam Marshall on Thursday morning confirmed he has the virus after dining with three Nationals colleagues on Monday night at an eastern Sydney pizzeria that was later declared a hotspot.

Trevor Khan, Steph Cooke and Ben Franklin have all since tested negative.

Mr Marshall issued a statement saying he had been isolating at his Sydney flat since Tuesday night and won't return to his Armidale home for at least 14 days. His staff are also in isolation.

Speaking to the ABC, Mr Marshall said he was physically fine and asymptomatic, but was concerned for everyone at parliament.

"It just highlights again everything that has been said about this new Delta variant is true," he said.

"The place where I caught it was a place where I had no physical contact with anyone at any time and yet I am now positive for COVID-19."

A Nationals budget dinner attended by Mr Marshall before he knew he was infectious on Tuesday night potentially exposed dozens of MPs to the virus.

Lower house Speaker Jonathan O'Dea on Thursday afternoon said no further MPs had tested positive, but some were still awaiting results.

Mr Marshall's infection sent shock waves through parliament, as premier Gladys Berejiklian warned the state was entering its "scariest" period since the pandemic began.

There were 18 new cases recorded from 48,402 tests in the 24 hours to 8pm on Wednesday, 13 of which were announced earlier.

Another six cases were detected after the 8pm cut-off which will be included in Friday's official tally.

That means there's a total of 11 new cases linked to the outbreak that began in Bondi last week that now stands at 36 after rapidly spreading in Sydney's east before infiltrating other areas.

Of the new cases, all but one are linked to a known case or the Bondi cluster, with urgent investigations under way into how a man in his 40s caught the virus. He's the second man in as many days who has contracted the virus from an unknown source.

Despite widespread speculation that Sydney was on the brink of another lockdown, the premier held her nerve but flagged a police blitz to nab anyone defying tough new restrictions announced on Wednesday.

"Since the pandemic has started, this is perhaps the scariest period that NSW is going through," she told reporters on Thursday.

"It is a very contagious (Delta) variant but at the same time we are at this stage comfortable that the settings that are in place are the appropriate settings, but that is so long as everybody does the right thing."

NSW Chief Health Officer Kerry Chant said a lockdown wasn't required because there weren't large numbers of unlinked cases nor a backlog of contact tracing.

Police also confirmed they were increasing compliance checks on mask-wearing and check ins, and would be out in force on the roads over the school holidays to ensure people weren't breaking orders not to travel outside of Sydney.

A ban remains in place for non-essential travel outside Sydney for people living or working in seven council areas that have been declared hotspots.

Masks are mandatory on public transport and at all indoor venues apart from homes, and homes have a five-person limit on visitors.

Australian Associated Press