A string of community transmission donut days in NSW has been a nice to see since a mystery COVID-19 case popped up in Sydney late last week.

However, despite its best efforts, NSW Health has not been able to find out how the case jumped from hotel quarantine into the community.

The man has clearly picked up the virus from a mystery person in the community, who could well have spread it to others.

So on today's Coronacast, how worrying it is that the link hasn't been found?

Also on today's show:

* The virus found in Sydney - B.1.617.2 - is declared a variant of concern by the UK Government

* Why don't these supposed very contagious variants seem to spread in Australia?

And don't forget to check out the new season of Patient Zero!

* Apple Podcasts: https://podcasts.apple.com/au/podcast/rn-presents-patient-zero/id1370255107

* ABC Listen app: https://abclisten.page.link/UgUg8Z4JtCaEh71p6