Queensland is watching the COVID-19 outbreak in NSW "very closely" as authorities continue to monitor quarantined passengers who arrived with Australia's first known case of the South African variant.
The state recorded two new virus cases on Wednesday, both acquired overseas and detected in hotel quarantine.
The pair had arrived from Pakistan and Ghana were not linked to the woman in her 20s who landed in Brisbane carrying the 501.V2 South African strain on December 22, a Queensland Health spokesman said.
Other passengers aboard the woman's flight were in hotel quarantine, he added.
She herself is in isolation at Sunshine Coast University Hospital, is asymptomatic and feeling well.
Standard COVID-19 precautions were being taken, including appropriate infection control procedures to protect treating clinicians.
Chief Health Officer Jeannette Young described the variant as "very concerning" and said the woman had been immediately quarantined.
Health Minister Yvette D'Ath said while other jurisdictions had detected a UK variant of the virus, this was the first time the South African strain had been confirmed in Australia.
"We are absolutely confident all proper measures were taken at the hotel and in the transfer, and of course at the hospital in relation to this positive case," she said.
Dr Young said the case posed "very low risk" to the community.
Even so, all other passengers aboard the woman's flight are in quarantine and being carefully monitored.
NSW reported 18 cases of community transmission and a second cluster in the inner west of Sydney on Wednesday.
Ms D'Ath said she was watching the situation "very closely".
"Queensland's Chief Health Officer is in constant contact with her NSW counterparts and receives regular updates on the growing COVID outbreaks in that state," she said.
"Queensland has strong border measures in place in response to the Sydney clusters, based on expert health advice."
Routine wastewater testing has also returned positive results for viral fragments of COVID-19 at seven treatment plants: Victoria Point, Oxley Creek, Goodna, Fairfield, Redcliffe, Cairns North and Nambour.
Dr Young said continued positive results, collected on December 22 and 23, are particularly concerning given the NSW cluster.
"We are concerned given this is the first time we've had seven locations test positive at the same time," she said.