The government says people in quarantine will be tested twice - firstly on day three and then again on day 11 of the 14-day quarantine period.

"Those who refuse to comply with testing will be required to remain in quarantine for a further 10 days to ensure they pose no risk of introducing coronavirus to the Victorian community," Premier Daniel Andrews announced on Sunday.

The decision follows a sharp spike in cases in Victoria, which is the only state to have reported cases in the double digits.

On Sunday, 49 new cases were reported - four from known outbreaks, 26 detected through routine testing while the other 19 were under investigation.

The premier confirmed the state's overall total cases increased by 41, with eight cases reclassified after further testing.

Four of Sunday's new cases are linked to outbreaks.

One is a case linked to a North Melbourne family outbreak, another is an employee at the Stamford Plaza Hotel, one is a close contact of a Brimbank family outbreak and the fourth is connected to the Coles distribution centre in Laverton.

Mr Andrews said 780,000 tests had been conducted in Victoria since January 1 and the new less-invasive saliva testing would start for those in hotel quarantine and hotspot areas from Sunday.

The original test involves swabs being taken from the nasal passage and back of the throat.

The premier said the saliva tests were a game changer, particularly as some returned travellers have been refusing tests, many of whom were parents of young children who did not want their kids undergoing the more invasive test.

Chief Health Officer Brett Sutton said it would not be clear for another five to six days how effective recent interventions have been in containing the virus.

Last week the government rolled back its decision to further ease restrictions in Victoria, including allowing only five visitors to a home.

Prof Sutton said if high case numbers continued, further revision could be made about restrictions.

"If it continues to increase, I think those are the circumstances where you think about an additional intervention and especially if it is localised in a particular postcode or a particular suburb," Dr Sutton said.

Health workers are going door-to-door in Keilor Downs and Broadmeadows, with mobile testing vans and expanded community engagement teams on the ground.

Residents in the two areas were also sent emergency text messages on Saturday, urging testing.

Mr Andrews said he wanted to avoid suburban lockdowns of badly-effected areas but it was still up for consideration.

"I hope it doesn't come to that ...That is not our preference, but we'll do it if we need to," he said.

Australian Defence Force medical and support personnel have arrived in Victoria to help the state's efforts.

There are currently 231 active cases in Victoria.

Seven people are in hospital with COVID-19, including one patient in intensive care while 1775 people have recovered from the virus.

Australian Associated Press