A woman who contracted the mutant UK strain of COVID-19 and flew into Brisbane from Melbourne after clearing hotel quarantine has since tested positive to the virus again, prompting an urgent public health response.

Under the previous national protocols, the woman was allowed to leave after 10 days in hotel quarantine, and did not need to return a negative test before doing so.

But because authorities are so concerned about this new strain, those rules have now been changed.

What do we know about this case?

Queensland’s Chief Health Officer Jeannette Young said the woman flew into Melbourne from the UK on December 26 and tested positive a day later.

She spent 10 days in hotel quarantine, “cleared all her symptoms and was allowed to leave Victoria”, Dr Young said.

The woman caught flight JQ570 from Melbourne to Brisbane, arriving at 11:00pm on January 5. She then travelled to her parents’ house in Maleny, on the Sunshine Coast.

Dr Young said Victorian authorities alerted their Queensland counterparts the woman had tested positive to the UK variant. She was retested in Queensland on Friday and found to still be positive.

It’s worth noting that authorities say she poses a very low risk, and they are contact tracing out of an abundance of caution because of this new strain.

Why are authorities worried?

The woman who left Melbourne contracted the same UK strain as the Brisbane hotel quarantine cleaner — whose positive result has sent Greater Brisbane into a three-day lockdown and seen borders slammed shut across the country.

Research estimates the UK variation could be up to 70 per cent more infectious than other strains, and authorities fear transmission could be hard to control if it gets into the community.

The UK strain is just one of a number of new variants of COVID-19 that appears to be more transmissible and therefore more concerning to authorities.

What rules are changing as these new strains emerge?

The guidelines from the Communicable Disease Network Australia have been updated to advise anyone who tests positive for the mutant UK strain to quarantine for the full 14 days from the onset of symptoms.

Friday’s National Cabinet meeting saw a number of other rules tightened to guard Australia against the strains.

International passenger caps have been reduced, masks are now mandatory in airports and on planes, tests will be compulsory before and after international flights and there will be daily tests for hotel quarantine workers.

The increased testing for quarantine staff was already in place in Victoria, which has dramatically overhauled its system in the wake of the state’s deadly second wave.