Mr Sharp said the health service would have a clearer indication of just where Shepparton is placed in the fight against COVID-19 in the next 24 to 48 hours.
Almost 5000 people across the Goulburn Valley have been tested for COVID-19 in a vast testing blitz after three new cases of COVID-19 were confirmed late Tuesday.
Roughly 96 per cent of tests from Wednesday have been returned, all with negative results, while results from Thursday's tests are expected to flow in throughout the day and into the night.
"We're optimistic to some degree that there hasn't been any further positive results since Tuesday afternoon," Mr Sharp said.
"But the next 24 to 48 hours are really important.
"As these results come in, particularly from yesterday and today's testing, (they will) give us an indication of just where we stand."
GV Health has increased the number of testing sites in Shepparton with support from health services in regional Victoria, Melbourne and the Australian Defence Force.
While crowds flocked to testing sites on Wednesday and Thursday, with some clinics reaching full capacity soon after opening, there have been minimal wait times at testing sites today.
But despite a sharp drop in the number of people attending the clinics, Mr Sharp was not concerned people were neglecting being tested.
He said people who have received testing after being identified as close contacts would now self-isolate until their subsequent day-11 test.
"But those people that are that are close contacts, they're staying at home ... and we're continuing to monitor them as well," he said.
There are currently 233 close contacts being monitored in relation to the Shepparton outbreak and roughly 150 secondary close contacts.
Mr Sharp said record keeping at businesses linked to the COVID-19 outbreak had been "a little bit variable", which may have slowed GV Health's contact tracing efforts.
"What we would ask people to do in terms of record keeping of businesses ... is to really focus on that," he said.
"When we have an outbreak like this, our contact tracing team needs information and they need it quickly.
"Having good record keeping only speeds up that process so it's really important that all businesses follow the guidelines that the state government has issued and keep those accurate records because we do rely on that information to move quickly in these circumstances."
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