Observations on the Current Outbreak of the SARS-CoV-2 Delta Variant in Sydney

Sydney, Australia, is currently experiencing an outbreak of the Delta variant of Covid-19. The Delta variant is much more transmissible than the original ‘wild’ variant of SARS-CoV-2, which was responsible for Australia’s first wave of infections, and for the second wave largely confined to Melbourne in mid-2020. Our purpose here is to compare growth rates for the current Sydney outbreak with those of the earlier outbreaks, using doubling times as the principal indicator. By such means, it appears that non-pharmaceutical interventions are achieving similar, if not stronger effects in containing Sydney’s Delta-variant outbreak.