An infectious diseases expert says there’s reason for concern over the source of the mystery cluster linked to a girl’s school in Sydney’s northwest. 

Overnight the state recorded 22 new cases, 8 linked to the Tangara School for Girls in Cherrybrook.

That brings the number of cases linked to the school to 17.

Infectious diseases physician and microbiologist Professor Peter Collignon told Jim Wilson while community transmission was still low in NSW, viruses are known to be transmitted more in winter.

“I think we need to be concerned: there’s ongoing transmission in NSW, admittedly at low levels but at level higher than what we’d like,” he said.

“It readily transmits between young adults if they are close together in a group.

“It could easily go out of control.”

He said avoiding busy, crowded public places where social distancing is difficult is an important measure.

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