Qld chief health officer Jeanette Young thanked the worker for coming forward to get tested.
"I don't think there's another cluster out there that we don't know about, but I need the genome sequencing," she said.
Authorities believed the cases were the UK variant, rather than the highly-contagious Delta strain currently spreading through Sydney.
Dr Young warned two cases had visited "a lot of sites throughout the community" while positive to Covid-19, including "several" gyms and shopping centres.
"There is a lot happening here, but the straightforward message is: please, if you are sick, it is absolutely critical that you immediately come forward, get tested and isolate till you get a negative result for Covid. That is just critical," she said.
A full list of sites visited by the two cases would be made public on the Queensland Health website.
Queensland had been easing out of restrictions, but developments in NSW have seen the one person per two square metre rule reinstated in pubs, nightclubs and cafes.
No more than 100 people would be allowed to attend private gatherings at homes.
The measures would last for the duration of Sydney's lockdowns.
Ms Palaszczuk said Queenslanders "owed it" to themselves, their families and their community to ensure the strain did not jump their southern border.
"If you are holidaying at the moment in New South Wales, you should reconsider that and think about returning home," she said.
"What is happening in New South Wales is very, very concerning. We haven't seen the likes of this before because this is the highly contagious strain."
NSW Premier Gladys Berejiklian, who has been reticent to impose lockdowns, has come under fire for being too slow to act on the latest outbreak.
Ms Palaszczuk, who has been at loggerheads with her NSW counterpart throughout the pandemic, did not criticise Ms Berejiklian directly but underlined the differences in the two states' approaches.
"We've always gone very hard and very quickly. That's always been our motto, and it's worked very well for Queensland," she said.
Anyone in Queensland who had been in the NSW local government areas of Woollahra, Randwick, Waverley or the City of Sydney since June 11 were required to remain at home for 14 days.
Dr Young warned there was "virtually 100 per cent transmission" of the Delta strain within households, arguing vaccination was the only form of protection.
"Everyone has got infected unless they were vaccinated. So vaccine is what we all need to do," she said.
Dr Young said the prospect of a hard border to NSW was a "possibility" and urged Queenslanders to reconsider their need to be in the state.
"It's always been a possibility right from the start of this pandemic … They might be facing 14 days' quarantine when they come back. They might be, we just need to work this through," she said.
The other case was a returned international traveller in hotel quarantine, which Dr Young described as "not concerning".
