STAFF and COVID-19 testing numbers have increased in Swan Hill following an outbreak in Mildura.

A man in his 30s tested positive at Mildura Base Public Hospital on Saturday after visiting the Melbourne Cricket Ground on July 10.

A total of four cases had been reported in Mildura by Thursday.

There were 11 COVID-19 exposure sites listed in Mildura, including one venue that was visited twice.

Bakery on Broadway in Wycheproof was listed as a tier 2 exposure site, which means anyone who visited on July 11, between 2pm and 3pm, must get tested urgently and isolate until a negative result is returned.

Swan Hill District Health (SHDH) chief executive Peter Abraham said testing at the Swan Hill drive-through clinic had increased to four hours a day to meet the demand for tests.

The health service has tripled its testing team to three, cutting down wait times.

SHDH staff tested 74 people on Monday, but people in five vehicles were asked to return on Tuesday to avoid testers having to work in the dark.

Testing at the McCallum Street site will take place from noon to 4pm up to this Sunday.

"If it gets really busy we will open up more," Mr Abraham said. "We sense (demand) will ease off a little bit."

"We think there will be an overflow from Mildura."

Mr Abraham said testing in Wycheproof was conducted by East Wimmera Health Service.

He said the health service was also testing asymptomatic interstate truck drivers and other workers where tests were warranted.

Mr Abraham said last week, before the Mildura outbreak, they tested about 30 people per day, an increase from about 10 per day.

He said the turnover for results was "relatively fast", usually within 24 hours but up to 48 hours.

Mr Abraham said having a positive case two hours away (in Mildura) was a wake-up call for people to continue wearing masks, socially distance and "everything else".

"It's the best protection we have," he said.

Several SHDH staff members travelled to Mildura on Tuesday to assist testing, while Mildura Base Public Hospital staff were in quarantine.

Robinvale District Health Services chief executive Mara Richards told The Guardian a record of 85 people were tested in Robinvale on Monday.

She said 50 people were tested on Tuesday.

As well as the public, Ms Richards said, about a dozen health service nursing and primary care staff were tested.

Sea Lake Health Service's Chevaun Wight said the service tested anyone returning from Mildura or Wycheproof who needed tests this week.

She more calls inquiring about tests on Monday.

"On Monday, we had an average of 20 (people getting tested), and on Tuesday and Wednesday, fewer than 10 -- that is pretty low for us," Ms Wight said.

"Due to minimal staff here, anyone we couldn't test we've advised to go to Swan Hill."

Ms Wight said tests included people returning to Mildura from holidays in Halls Gap, from Wycheproof, Sea Lake and district and Mildura.

In the fourth day of drive-through testing in Mildura, about 2670 tests had been conducted.