Victoria has posted another 80 local coronavirus cases, including 41 who were not isolating while infectious.

The daily tally is the highest yet in the state’s Delta outbreak and takes the total number of active cases in the state to 618.

Sixty-seven of the latest cases are linked to known sources.

The burgeoning COVID outbreak has hit Victoria’s health system and is causing distress in the regional town of Shepparton.

The state’s exposure sites list has ballooned past 800, including the emergency department of Monash Medical Centre. It is listed as a tier one exposure site.

• See all of Victoria’s COVID exposure sites here

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Victoria is recruiting 350 overseas doctors and nurses to ease pressure on a hospital system as it faces hundreds of workers being furloughed due to coronavirus exposure, including at Royal Melbourne Hospital and Goulburn Valley Health.

The Goulburn Valley is battling an outbreak centred in Shepparton with at least 50 cases and a third of the town’s residents in isolation.

Among those told to quarantine are supermarket staff, prompting many shops to close for cleaning, limiting access to essential supplies.

Greater Shepparton mayor Kim O’Keeffe said the central Victorian town needed immediate support.

“We have so many shops in our hot spots that are closing. We have supermarkets that don’t have enough staff, with over 20,000 in isolation, many being workers and students, so we are in need of extra support,” she told the ABC on Thursday.

“Our local health hospital here, they are down 450-plus numbers of staff. We need support in the health system.”

About 50 Australian Defence Force troops are expected to arrive in Shepparton on Thursday.

The spike in local virus cases came after cases fell to 45 on Wednesday. But Victorian authorities warned even then that people were still taking too long to get tested – and that the continued high number of mystery cases remained a major concern.

“Some of the recent cases … haven’t been tested for seven or eight days,” health official Kate Matson said on Wednesday.

“If we don’t know about it, we can’t isolate it.”

Meanwhile, more than 95,000 Victorians booked vaccine appointments at state-run hubs to 4pm on Wednesday, despite the online system being overwhelmed as Pfizer eligibility expanded to those aged 16 to 39.

Victoria’s lockdown is due to last until at least September 2.

-with AAP