What is the Source of Sydney’s Covid-19 Outbreak?

The index case for the 83-case outbreak on Sydney’s Northern Beaches remains unknown as of Monday night, five days after the initial positive test reports. Genomic testing suggests the airport shuttle bus driver and the Avalon couple were infected with different strains of the virus.

How did the Northern Beaches cluster start?

Two separate sets of positive tests were first reported last Wednesday. One was an Avalon couple, the other a shuttle bus driver doing airport shuttles. The van driver who drives a shuttle bus from the airport to hotels also tested positive on Wednesday. However, despite testing positive on the same day, the cases do not appear to be linked.

One traveller, who arrived in Sydney from the US on 1 December, is Covid-positive and still in quarantine, is being considered a potential index case. But it is still not yet clear how the virus reached the Northern Beaches.

The virus currently circulating in Sydney is a strain that is also currently circulating in the United States. It is different from the virus contracted by the shuttle bus driver.

There appears to have been a superspreading event (a phenomenon we covered here) in several Avalon venues on 11 December. NSW Chief Health Officer Kerry Chant: “Our working hypothesis is that someone at that RSL club was potentially the source of infection for a number of subsequent cases,” Dr Chant said. It is not entirely clear who is the index case for the infections that occurred at the Avalon RSL.

The Avalon RSL

The virus quite likely arrived with international air crews, either residing in the Northern Beaches area or overseas crew who have already left. Quarantine restrictions have previously been lax for airline staff. They are expected to stay at the hotel accommodation arranged by their employer and remain there until their return flight. They have been allowed to make their own way to their hotel, including via Uber or taxi. 

On a flight that arrived in Sydney from South America on 5 December, a group of 13 staff left their Mascot hotel and went out to local venues. They were each fined $1,000 for breaching public health directives. From today, air crew will be confined to police-monitored hotels at the airport, a welcome shift that will mark one positive that we can take out of the current outbreak.