NSW Health is investigating the source of a COVID-19 case diagnosed in hotel quarantine which has an identical viral sequence to two cases who were staying in an adjacent room.

It is currently unclear how and where transmission occurred from a couple to another returned traveller who were all staying on the fourth floor of the Radisson Blu quarantine hotel.

Genomic sequencing has shown all three cases have identical viral sequences of the Alpha strain (B.1.1.7).

The couple, who were asymptomatic, tested positive to COVID-19 on a routine Day 2 test on 3 June.

The other returned traveller – the secondary case – returned a negative Day 2 test on 3 June before subsequently developing symptoms and testing positive for COVID-19 following a test on 5 June.

The couple and the secondary case were transferred from the Radisson Blu to the Special Health Accommodation, where they remain, following their positive tests.

All three cases arrived into Sydney on the same flight from Doha on 1 June and stayed in adjacent rooms in the quarantine hotel.

Early possibilities as to where transmission may have occurred from the couple to the secondary case include on the flight, on transport from the airport to the hotel, in the lobby of the hotel, or while in quarantine. Currently, there is no evidence of further transmission.

While the investigations into the transmission continue, out of an abundance of caution, all returned travellers who were on the same floor of the Radisson Blu hotel between June 1 and June 5 and were subsequently discharged are being contacted and asked to get tested and isolate at home pending further advice from NSW Health.

NSW Health has also asked all staff who worked on the fourth floor between June 1 and June 5 to get tested and isolate pending further advice from NSW Health.

All staff working in NSW quarantine hotels undertake regular rapid saliva testing as part of COVID-19 surveillance testing.