It is the first time in months that a known case is confirmed to have been in the ACT, however authorities are saying the risk to Canberrans is low.

ACT Health said the woman in her 30s transited through Canberra Airport on October 7 while travelling from Townsville to Melbourne.

"The individual, who tested positive three days after arriving in Melbourne, was asymptomatic during her stopover at Canberra Airport from 8.30am and 10am and wore a mask on all flights and in the airport," ACT Health said in a statement.

"ACT Health is working with public health units in Victoria and Queensland to investigate and confirm her source of exposure, and contact tracing of flights is under way. This work is taking place in line with national public health guidelines.

"ACT Health is contacting passengers and crew on flight QF1543 from Brisbane to Canberra, who may have been in close contact with this particular passenger.

"As a precaution, we are also advising anybody who was in the Canberra Airport at Gate 13 or 14 during this period to watch for symptoms and if symptoms develop, isolate and get tested for COVID-19."

ACT Health said there was a low likelihood of virus transmission in this instance, but it was a timely reminder that COVID-19 was still here and the situation could change quickly as borders begin to open across Australia.

It is also important that people take appropriate precautions while travelling.

An ACT Health spokesperson said flight QF1543 had 91 passengers on board, and a small number of close contacts had been identified. All of those people have been contacted.

"ACT Health and Canberra Airport are confident in the airport's current COVID-19 health and safety processes and procedures," the spokesperson said.

"No other flights into Canberra have been impacted."

ACT Health said contact tracing for the woman's second flight, Flight QF2149 from Canberra to Melbourne, is being managed by Victorian public health authorities.