He repeatedly tested negative to coronavirus while quarantining in South Australia and only developed symptoms on May 8, after he was released and was in Melbourne.
Authorities say he visited several locations across Melbourne and may have been infectious since May 6.
After experiencing two new local cases of the virus in Sydney’s east last week, New South Wales is determined not to let anymore cases cross the border.
A border declaration system is in place for anyone travelling from Victoria, meaning travellers must confirm they have not been to any of the potential exposure sites in Victoria.
NSW Health says anyone arriving from Greater Melbourne must complete a declaration confirming they haven’t been to any of the exposure sites.
Anyone who arrived from the Greater Melbourne area since Thursday, May 6 are required to check in with the Victoria Department of Health and Human Services website and immediately follow the outlined public health advice.
If a person has visited any of the potential exposure sites, they must also contact NSW Health on 1800 943 553.
“This form includes contact details and confirmation of whether people have been to any venues of concern,” NSW Health tweeted.
“Declaration forms must be completed within the 24-hour period prior to entering NSW, or on entry to NSW.”
South Australia is urging anyone who visited any of the locations specified by Victoria Health as potential transmission sites to quarantine immediately and get tested for coronavirus on arrival into the state.
Anyone who has been in Victoria since May 6 should also monitor for symptoms and get tested if any develop, no matter how mild.
While SA authorities are still investigating how the man contracted the virus, they say it is not believed he was infectious while in the state.
Queensland Health is advising anyone who has been to an exposure site in Greater Melbourne who is already in the state or who will arrive in Queensland before 1am, Thursday, May 13 to immediately contact 134 COVID and travel to your place of accommodation by private transport and quarantine for 14 days from the time you arrived at the venue.
Anyone arriving in Queensland after 1am on Thursday, May 13 who has been to a Greater Melbourne exposure site will be required to undertake mandatory hotel quarantine for 14 days.
Anyone who recently arrived in Queensland from Victoria or South Australia and hasn’t visited any of the potential exposure sites is asked to get tested for COVID-19 and isolate until they receive a negative result.
Western Australia’s Chief Medical Officer, Dr Andrew Robertson, said anyone who visited a potential exposure site in Greater Melbourne at the times indicated should get tested for coronavirus immediately and quarantine for 14 days from the date of exposure.
Dr Robertson said the risk to WA was low, but authorities would monitor the situation and change precautions if deemed necessary.
“We believe any risk to WA remains very low,” he said.
“However, the situation highlights the importance of remaining vigilant to prevent any spread of the virus or community transmission in this State.
“We will continue to monitor the situation in Victoria very closely and issue updated health advice if required.”
Anyone wanting to enter Western Australia, Queensland or the Northern Territory from Victoria must quarantine for 14 days if they have been to any of the alert zones.
Victoria has held off implementing any restrictions, despite news of the new case.
Victoria’s Chief Health Officer, Professor Brett Sutton said the state needs to be “alive to the possibility” of infection still being a threat.
“We are not foreshadowing anything,” he said.
“People should wear masks when they can’t physically distance from others, especially in indoor settings.
“We know it is mandated on public transport, airports, rideshare vehicles, so people should absolutely follow those rules.”
A new list of locations has been released, linked to the positive local case.
SMS messages were sent to people in Greater Melbourne warning anyone who has been to one of the “tier one” sites to isolate, get tested and then continue to isolate for 14 days even if they test negative.
People affected have been asked to call the Department of Health on 1300 651 160.