The highly infectious SARS-CoV-2 Delta variant cluster in Victoria may never be linked to a known source because of inherent limitations to genomic sequencing, a leading infectious diseases expert says.

Melbourne’s outbreak continues to grow amid new warnings the Delta ‘variant of concern’ — now the dominant strain in the UK and India — is about 40% more infectious than the Alpha (UK/Kent) variant.

Victorian health authorities say there has been 11 new cases recorded in the past 24 hours, taking the number of active cases in the state to 81, excluding hotel quarantine, and these include 14 Delta cases.

The larger Kappa variant outbreak has already been linked to a leak in SA hotel quarantine, but the source of the Delta variant in the West Melbourne cluster is yet to be identified.