There are concerns after a “highly unusual” test result saw a woman spend more than three days out in Melbourne while infectious with Covid-19 after she attended a party.
Victoria is in day two of its five-day lockdown with 22 confirmed active cases of community transmission, 16 of which are connected to an outbreak at the Holiday Inn at Melbourne Airport.
One of the positive cases is a woman who worked for Covid-19 Quarantine Victoria (CQV).
As part of her job, she is regularly tested for coronavirus and returned a negative test result on Sunday last week.
However, testing commander Jeroen Weimar said that test result was reviewed on Wednesday and she returned a weak positive.
The woman also attended a private function at a venue in Coburg on February 6.
“There was a staff member there who was not known to be positive at that time who attended that venue, that family event with household members, two household members at least and number of other people,” Mr Weimar said.
“There were 38 in total associated with that extended event. All of those people have been tested and there are a number of positive cases that have come out of that have now been traced back to that event.”
Mr Weimar added the positive tests included the woman, her housemate and a child aged 3.
The child’s mother has also returned three different test results in the past 24 hours.
“Serology is being done and we will work out over the next few hours exactly where this individual stands,” Mr Weimar said.
He said the CQV worker was likely a positive case on February 6 and 7 after contracting the virus on either February 3 or 4.
“The genomics is clear that it is all part of the same strain and comes back to the individual index cases we've talked about in the hotel,” he said.
False negative Covid tests are rare, CHO says
Chief Health Officer Brett Sutton said cases of false positives or negatives were rare.
“It is highly unusual to get a negative test on someone who was later found to be positive and, in fact, transmitted to other people,” Professor Sutton said.
“To be a weak positive but to pass on to others is unusual.
“But we have to be agile in our response and understand that that was a transmission event, and wrap the public health response around everyone who was there.”
When pressed about a delay in contacting the quarantine worker, Prof Sutton said: “What do you expect us to do?
“We do not have exposure sites for people who return negative tests.
“All we can do is remain alert to any other result that comes through, to investigate those results, to find out how transmission might have occurred and to wrap the public health response around those close contacts which is exactly what we've done.”
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