Sydneysiders are again wearing masks on public transport, in supermarkets and during ride share trips as health officials try to figure out how a strain of COVID-19 escaped hotel quarantine.

It comes as NSW recorded no new community-acquired cases of COVID-19 overnight, and health authorities continued to search for the missing link between a traveller from the United States and an infected Sydney couple. That will keep other potential interstate travel restrictions on hold for the time being.

Restrictions for Greater Sydney were reimposed on Wednesday, including mandatory masks in indoor settings, a 20-person cap on indoor gatherings, and a ban on singing.

A health alert was issued on Thursday evening for Haymarket restaurant XOPP. Diners present between 1.30 and 2.30pm last Wednesday must be tested and self-isolate until they’re negative. Health authorities are concerned the compliance with check-in procedures at the restaurant may be low.

A number of places have also been listed as sites where fellow attendees are close contacts who must isolate for 14 days, including the exclusive Royal Sydney Golf Club, a CBD optometrist, and other venues in Paddington, Rushcutters Bay, Moore Park and Collaroy.

Other places – including a number of barbecue shops throughout Sydney – are lower-risk, with fellow visitors asked to isolate until they receive a negative result.

Queensland police and health officers have been meeting flights from Sydney to question travellers about their movements and direct anyone who has been to exposure sites into hotel quarantine.

New Zealand has blocked NSW residents from being part of the trans-Tasman travel bubble, which has reportedly affected outbound flights from Gold Coast airport.

Ahead of the news of no new cases being found in the community, Premier Gladys Berejiklian on Friday said she was “pleased” with the current state of the outbreak.

But the missing epidemiological link between the infected east Sydney man – who subsequently infected his wife – and a coronavirus-positive traveller in hotel quarantine remains unclear.

The pair are infected with the same COVID-19 strain.

“The only concern for us is obviously the fact that at least one person has been in the community going about their business for a few days, having the virus and not knowing they have it … it could be more than one,” Berejiklian told the Nine Network.

“We’re just saying to people: go about your daily business, just be extra safe.”

New Zealand called a time-out on the travel bubble with NSW on Thursday, suspending quarantine-free travel from the state for 48 hours from Friday.

The relative idyll in NSW was broken after the east Sydney man, aged in his 50s, tested positive for the virus on Wednesday.

Berejiklian urged businesses to stay open and Sydneysiders to show up for their Mother’s Day reservations on Sunday.

“Every time we go through this in NSW, we learn from what we experience, learn from what we did well or didn’t do well, then we can apply it into the future,” Berejiklian said.