Sydney COVID-positive man had visited ACT

Canberra authorities have issued a public health alert after a Sydney man who tested positive for coronavirus visited the national capital on the Queen's Birthday public holiday.

The man in his 40s visited Canberra on Monday and went to the Botticelli to Van Gogh exhibition at the National Gallery of Australia between 12 and 1.45pm.

From there, he went into town and dined at the Via Dolce cafe in Civic between 2.45 and 3.15pm.

Anyone who visited those locations at the same time has been told to isolate, get tested and fill in an online declaration form.

ACT Health is expecting the list of exposure sites to grow as investigations continue.

Meanwhile, a delegation who attended the G7 summit has returned to Canberra and entered quarantine.

The group of about 40 people who went to Europe and Singapore will isolate in Canberra for 14 days.

They include staff from the prime minister's office, officials and journalists.

Prime Minister Scott Morrison will be allowed to quarantine at The Lodge.

About 30 others will isolate in empty student accommodation at the Australian National University, while 10 others quarantine at home.

The university is being used because the hotel previously used for returning travellers has returned to regular service.

The fortnight is considered an unofficial trial for the return of international students.