Bad luck or bad management: why has Victoria had so many Covid outbreaks?

Medical experts explain how much quarantine breaches, cold weather and pure chance contribute to the spread of coronavirus cases in Melbourne

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Victoria has started its seven-day circuit-breaker lockdown - its fourth lockdown since the coronavirus pandemic began.

Other states have also imposed snap lockdowns or restrictions as a result of Covid cases in the community, most recently New South Wales, after a mystery case. But, with the exception of Sydney's northern beaches cluster, most leaks from hotel quarantine have not resulted in sizeable outbreaks.