Sydney's CBD coronavirus cluster has grown over the weekend, with more people being diagnosed with COVID-19 and being linked back to a city fitness centre.

A health notice was issued on Saturday for people who attended the Tattersall's fitness centre at certain times over five days in middle to late August.

There are also alerts for other gyms in the city, after an infected person visited them last week.

So are gyms becoming coronavirus hotspots and are they any riskier than other indoor environments?

On today's show:

* Is there something that causes gyms to be a riskier venue than other places?

* So should I avoid the gym and just stay home and watch TV?

* What about runners or people exercising outdoors?

* What can gyms tell us about how coronavirus spreads?

* What's happening with the healthcare worker numbers in Victoria?

* What's going on with China's authorisation of a vaccine for emergency use?

* Have there been any studies into the effect of climate or weather and COVID-19?