THE TRAVELLER AND THE NURSE:
Authorities believe a nurse at Brisbane's Princess Alexandra Hospital became infected during an overnight shift that ended on March 24.
She had been working on the hospital's coronavirus ward, where a man who'd recently returned from India was being treated.
Genomic sequencing later proved the nurse was infected by that traveller.
The nurse subsequently infected her sister.
THE HENS PARTY IN BYRON BAY:
The nurse and her sister then travelled to Byron Bay for a hens night. They did not realise they were infected.
In total, 11 people from Queensland attended that party last weekend - 10 guests and a Gold Coast tradie who was moonlighting as an entertainer.
Seven have since tested positive for coronavirus - six guests and the tradie. The other four guests are negative so far but remain in quarantine pending further tests.
The Queensland group stayed in a house but visited several Byron Bay venues which are now considered exposure sites.
The tradie visited an aged-care facility after returning to the Gold Coast. Authorities hope the risk is low because all residents had received their first vaccine shot.
Coronavirus cases linked to the hens night are being treated at hospitals in Toowoomba, Bundaberg, the Gold Coast and Brisbane.
CHANCE ENCOUNTER AT BYRON BEACH HOTEL:
The Byron Beach Hotel is among the venues visited by the hens group.
A man who sat about three metres from them has also been infected, NSW authorities said on Wednesday.
He came forward for testing after hearing about the hens party infections.
Before he tested positive he had travelled to locations in Ballina and East Ballina.
So far three friends he was with at the hotel have tested negative.
THE SECOND NURSE AND HER FLATMATE:
On Wednedsay, Queensland authorities revealed there were two more cases of community transmission that could be linked to the traveller who returned from India.
One is a nurse who also works at the Princess Alexandra Hospital's coronavirus ward. The other is her flatmate.
Genomic sequencing for one of those two new cases has proven the link with the traveller from India and therefore also the first infected nurse, and the hens night group.
The second infected nurse did not directly treat the traveller from India.
Authorities suspect environmental contamination or "aerosolisation" of the virus. The hospital has been locked down, with deep cleaning of the coronavirus ward underway.
The second infected nurse received her first vaccination shot on March 19. Authorities say she wouldn't have had any significant immunity until a week later, on March 26.
She has not had a second shot, required three weeks after the first. It's the second shot that provides maximum protection.
WHAT NEXT FOR QUEENSLAND'S HOTSPOTS:
Greater Brisbane remains under lockdown, but might escape the stay-at-home directive in time for Easter.
The lockdown is due to end at 5pm on Thursday.
Whether that lifts will depend on any new infections that cannot be linked to known cases.