Several cases of community transmission of coronavirus have been detected in Melbourne, as authorities rush to identify exposure sites and close contacts.

While we brace for more cases, much is still unknown, such as where the virus came, its genomic information and how many missing links there might be.

Victoria's Chief Health Officer Brett Sutton says it's a concern as we head into the winter months, as people are more indoors where we know the virus is far more likely to spread.

Also on today's show:

• More on the British vaccine and data that were discussed yesterday. It seems Astra might not be as effective as hoped, but could mixing it with a Pfizer booster shot make it better?