"The unexpected detections may be due to a person or persons with Covid-19 being in the early active infectious phase or it could be because they are continuing to shed the virus after the infectious period," the health department said in the alert. "While it is possible that these detections are due to a visitor or visitors to these areas who are not infectious, a cautious approach is being taken." Mackenzie Sweetnam/Getty Images The alert comes as Victoria today launched three mass vaccination hubs. The Royal Exhibition Building, Melbourne Convention and Exhibition Centre and Geelong's former Ford factory will provide AstraZeneca shots for anyone over 70 with or without bookings.