Queensland authorities are concerned a COVID-19 "superspreader" may have passed on the virus to people on an international flight and possibly in hotel quarantine.
The state reported seven new cases on Thursday, two of whom were in quarantine after arriving on a Qatar Airways flight in Brisbane on February 17.
Four other people on that plane have already tested positive for the new Russian variant COVID-19.
Queensland Health is testing another 72 people who were on that flight and has ordered them to extend their 14-day quarantine by five days.
Chief Health Officer Jeannette Young says one man seems particularly contagious and she's concerned he may be a "superspreader".
"We've had plenty of people throughout the pandemic who've been super spreaders. We had one individual who managed to spread it in a few hours to 40 other people for instance, so we've had super spreaders all along from day one," she told reporters.
"So it's the fact that there's been spread on that plane, there's no doubt about that. That is the concern, it's not that it's the Russian variant."
The chief health officer is confident the virus was spread on the plane by someone who had the disease prior to boarding in Doha.
However, she's concerned one transmission could have happened between two people quarantining in adjacent rooms on level eight of the Mercure Hotel in Brisbane.
"It could have happened, unlikely, but it could have happened in the hotel, because this person was in the room next to the person who was positive," Dr Young said.
Authorities are now racing to contact another eight people who were staying the same level of the hotel between February 17 and 21.
Dr Young said those people may be in other states outside Queensland and she has alerted the national incident room.
The other five new cases reported on Thursday were workers who arrived in Cairns on a chartered flight from the Ok Tedi mine in Papua New Guinea.
Dr Young said more than 500 people including locals and foreign workers at the gold and copper mine have been infected with COVID-19.
The continuing cases arriving in Queensland from Ok Tedi have strained local healthcare capacity in Cairns.
Dr Young said Ok Tedi Mining Ltd had suspended the flights for the next week at least.
"We've been working with the Ok Tedi mine to work through that because we've seen a lot of positive cases come from there," she said.
"Most of them have been treated in Cairns and that's pushed the resources."
Health Minister Yvette D'Ath said 5409 people have been given their first dose of the Pfizer vaccine against a target of 3000 at this stage.
She also defended a Tweet from the official Queensland Health account saying it was "being picked on" about the slow vaccine rollout compared to other states.
"What it shows is probably a bit of frustration," Ms D'Ath said.
"There was some reporting at the start of this week saying that Queensland Queensland was falling behind and slow in its rollout.
"None of that's accurate"
Australian Associated Press