The three new cases are likely unrelated to recent outbreaks in Queensland – two are suspected to be the result of a Sydney hotel quarantine breach – prompting Chief Health Officer Jeannette Young to order masks remain for another week.

Restrictions were due to be eased at 6am Friday but Young said contact-tracers needed time to track the movements of the new cases and isolate all close contacts. Only Townsville and Palm Island will have restrictions lifted as planned tomorrow.

It is not yet clear whether the new cases involve the more contagious Delta variant of COVID-19, however ongoing outbreaks in Sydney and Melbourne have Queensland Health on high alert. Brisbane and Townsville were only recently in lockdown after the emergence of the Delta threat.

The travellers were a 12-year-old boy and his mother from Newport, who travelled to the United States for three months and completed 14 days hotel quarantine in Sydney upon their return.

They flew Qantas to Brisbane on July 9, where they were greeted by the boy’s father. This week, the boy became ill, prompting a visit to a doctor and chemist at Aspley, and test results last night revealed he had COVID-19 – and so too did his father. His mother has so far tested negative but is with the boy in hospital.

“He’s acquired it in Sydney,” Young said, as she awaits genome sequencing and the boy’s test results from NSW Health.

The boy has not been to school this week, while his father works in a financial services firm at Cotton Tree on the Sunshine Coast.

The third confirmed case of community transmission is a woman in her 40s who lives at Tarragindi and works at Brisbane International Airport. She became unwell on Tuesday and got tested on Wednesday, and is now known to have visited a Woolworths and Chemist Warehouse at Annerley while infectious.

Young praised the woman for being fully-vaccinated with Pfizer and using the Queensland check-in app, but was “very concerned” she may have passed on the virus during three days working at the airport.

“We now have to see where they’ve been working, who they’ve come into contact with – there’s a significant risk there,” Young said.

Young said that while the vaccination rollout was continuing at the airport, she had been there a few times in recent months “and not everyone is wearing masks,” despite them being mandatory.

Two other cases have been confirmed in international travellers already in hotel quarantine, bringing the Thursday total to five, with 50 active cases in Queensland.

Premier Annastacia Palaszczuk said keeping masks mandatory in Greater Brisbane for another week would help protect the community from any outbreak.

With a more dire situation in Sydney, and now also in Melbourne, Palaszczuk repeated her call for Queenslanders to reconsider travel to NSW and Victoria and come home if possible.

“We are seeing these little spot fires happening across the nation,” Palaszczuk said.

Under the restrictions, visitors will also remain barred from entering hospitals, aged care and disability services, and social distancing provisions will stay in place, in the Brisbane, Moreton Bay, Ipswich, Logan City, Redlands, Sunshine Coast, Noosa, Somerset, Lockyer Valley, Scenic Rim and Gold Coast council areas.