WASTEWATER testing detected fragments of COVID-19 in the Swan Hill and Woorinen South areas on Thursday night (October 7), but no exposure sites have been listed.
Contact tracers are continuing to investigate its link to any COVID-19 cases.
Swan Hill District Health chief executive Peter Abraham said Swan Hill District Health (SHDH) received notification on Friday morning about the result.
"The wastewater detection is a really strong indicator that there is currently, or has been, COVID-19 in the community," Mr Abraham said.
"It's a detection of the shedding of COVID-19."
SHDH received the information from the Victorian Department of Health and Human Services.
Mr Abraham said numbers of cases from Mildura to New South Wales were growing and with border restrictions easing it was likely COVID-19 could emerge in the Swan Hill region.
"With wastewater detection, it's more than likely that cases will appear," he said.
Mr Abraham said there were three things people could do to protect themselves.
"If anyone has symptoms, they should get tested.
"This doesn't mean people should be concerned – only get tested if you have symptoms.
"SHDH will continue to operate the Swan Hill drive-through COVID-19 testing clinic on McCallum Street daily from 9am to 1pm, but we are always ready to extend the hours if needed."
Mr Abraham said the second thing residents could do was to get the COVID-19 vaccination.
"We are doing more than 150 vaccinations per day (at the Swan Hill Commonwealth Vaccination Clinic), but there are five other vaccination sites in Swan Hill, so there is plenty of opportunity," he said.
Last weekend about 95 per cent of people aged 15 and over had had their first dose of COVID-19 vaccine in the Swan Hill local government area and 58 per cent had had their second.
Mr Abraham said people should continue to follow the precautions.
"If you're going to wear a mask, wear it properly – wear your mask above your chin and nose," he said.
"And follow the 1.5-metre rule."