Covid 19 coronavirus: Sydney put on alert after worrying virus warnings

After a weekend of sunny weather in Sydney, the city has now been put on alert with a series of worrying virus warnings.

Yesterday, new cases were confirmed at a childcare centre and shopping mall on Sydney's north shore and an urgent warning was issued for bus commuters to isolate immediately amid a growing cluster in the city's eastern suburbs.

There are now warnings in place across the city after recorded cases visited shopping centres, pubs and gyms. A school and an early learning centre have also closed.

The latest affected locations are Chatswood Chase shopping centre, St Paul's Catholic College in Greystanes, Reddam Early Learning Centre at Lindfield, Highfield Caringbah pub, Fitness First Randwick and Broadway shopping centre in Ultimo.

NSW recorded seven new Covid-19 cases on Sunday, including a student at a western Sydney school and five linked to the CBD cluster, which has grown to 28.

'Probably not' the time for mandatory masks in Sydney

There are growing calls for mandatory mask use on public transport in Sydney after a scare involving two infected bus passengers on a popular route.

However, federal Deputy Chief Medical Officer Nick Coatsworth said it was unlikely health authorities in NSW and Queensland would make masks mandatory in the immediate future.

He told the Today show he doubted the logistical trouble of having an enforcement mechanism was worth the benefit.

"You have to get to the point where it's actually going to make a substantial difference to transmission," he said. "And that's probably not at the level that NSW has had at the moment."

Investigators are scrambling to track down passengers on the X39 Sydney Buses service that left Pitt St opposite Australia Square in the CBD at 6.08pm and arrived at Clovelly and Carrington Rds at Randwick at 6.40pm on Thursday, August 20 after two commuters later tested positive.