The number of COVID-19 cases linked to the south-western Sydney pub was at 34 on Wednesday, with concerns the virus may have spread to more venues.

Venues including the Milky Lane burger restaurant in Parramatta, steakhouse Hurricane’s Grill in Brighton and Woolworths at Bowral in the Southern Highlands.

NSW Chief Health Officer Dr Kerry Chant said several of the 34 cases from the Crossroads cluster had developed their COVID-19 symptoms incredibly fast.

She said while the incubation period for COVID-19 is usually within 14 days, “people have developed the symptoms, more towards the one day period than the 14[days]”.

“It gives you very little time for the contact tracers, because you’ve got to get your cases diagnosed and then you’ve got to lock down those contacts,” Dr Chant said. “If you’ve got a sore throat today, don’t wait for two days to get it diagnosed. Work with us. Go get tested day one because every day you can give us allows us to to stop that spread.

“I am far from relaxed. This is a critical period for us and I need the co-operation of the public.”

Genome sequencing has confirmed the Sydney cluster is linked to Melbourne’s outbreaks in a clear sign the virus has seeded from Victoria, which recorded 238 new cases on Wednesday.

Virus detectives have identified patient zero from the Crossroads outbreak as a Melbourne freight worker who infected several colleagues at their workplace before they all attended a dinner party at the south-western Sydney pub.

NSW’s COVID-19 operations manager and epidemiologist Jennie Musto said the first clues were supplied via two simultaneous interviews of seemingly unconnected cases.

A man in the Nepean told contact tracers he had been to the Crossroads Hotel, and a woman told tracers at Liverpool Hospital she had also had dinner at the venue.