An aged care worker at a facility in Melbourne’s west has been diagnosed with COVID-19, sending the home into lockdown.
The worker at Arcare Maidstone was one of five locally acquired COVID-19 cases across Victoria reported Saturday.
The healthcare worker was not showing symptoms when she last worked at the home on May 27, but later tested positive, Arcare said.
She had received a first, but not a second, dose of a coronavirus vaccine.
Both the Pfizer and AstraZeneca vaccines offer a level of protection against serious illness after the first dose, but it is not unexpected for people to still be able to contract the virus.
Two of the other five new confirmed infections were identified as close contacts of existing cases and were already in quarantine.
A third was linked to a Telstra store in South Melbourne, one of the more than 170 exposure sites connected to the cluster, and so was already isolating.
The source of the aged care worker’s infection is not yet known.
“This aged care positive case is of extreme concern to us,” COVID-19 response commander Jeroen Weimar said.
“For two reasons: One, it’s our most vulnerable and sensitive setting … [and] I am concerned that we don’t have at this point in time an acquisition source.”
The worker is being treated as a “mystery case”, the first of the current outbreak, until the source of the infection is found.
“This is the biggest priority for us to understand,” Mr Weimar said.
Genomic sequencing is currently underway to trace the source of her infection.
The outbreak, which has led to a lockdown, started with a Wollert man who contracted the virus in a South Australian quarantine hotel.
However, health teams are still yet to directly link him to the other cases in the cluster, leading to concern the virus may have been spreading undetected in the community.
The five local infections and an overseas-acquired case in hotel quarantine were detected from 45,301 test results processed on Saturday.
There are now 49 active infections in the state, including those in hotel quarantine.
There were 17,702 vaccine doses delivered in state-run centres on Saturday.