Victoria now has 21 coronavirus cases after three more people tested positive overnight, including a man who worked at a Melbourne school while infectious.
One case is a man in his 50s who returned to Melbourne from Seattle on Saturday, March 7, on Virgin flight VA24.
Authorities say the flight manifest is being obtained so passengers in the same and adjacent rows can be traced and contacted.
He became unwell on the same day he arrived home and is now recovering in home isolation.
Three close contacts, including two children, are being supported and are self-isolating for 14 days.
Before being diagnosed the man visited the Mussel and Jazz Festival at South Melbourne Market on March 7 between 2pm and 3.30 pm, then went to the Rebels and Lions rugby match at AAMI Park where he sat in section 9.
The two other cases were on flights from the USA, which have had confirmed COVID-19 cases in passengers this week (UA0600 and QF94).
Both cases are recovering in home isolation and acquired the virus in the USA.
One of those cases is a staff member at Yeshivah and Beth Rivkah Colleges at St Kilda East, who worked for half a day while infectious on Monday.
The man in his 50s returned on flight QF94, Los Angeles to Melbourne, on Friday morning.
"As a result, we have closed the school for 24 hours to assess the situation," the colleges said in a statement.
The closure applies to the boys' and girls' campuses, including the early learning centre and creche, and the Yeshivah Centre.
The college is working with the health and education departments to map the potential spread of the virus within the school.
Students from the college are also being tested, with results due on Wednesday.
The closure follows that of Carey Baptist Grammar School in Kew for the week following a teacher testing positive.
The third new case is a woman in her 20s who travelled to multiple places in the United States and became unwell on February 29, after returning to Melbourne on the same day.
The health department is contacting her close contacts to get them to self-isolate for 14-days.
Seven COVID-19 screening clinics are now open in Victoria, including one at the Royal Melbourne Hospital, where lines of people in masks could be seen awaiting tests on Tuesday.
One Melbourne doctor - former Australian Medical Association president Mukesh Haikerwal - has resorted to screening patients in cars outside his Altona North practice.
Victoria's dedicated COVID-19 phone line and the Nurse-On-Call Hotline both crashed on Tuesday due to an influx of calls.
Another 50 staff will be brought on deck for the coronavirus helpline on Wednesday, with an additional 100 by week's end.
© AAP 2020