Mistakes in a Sydney laboratory that led to nearly 1,000 people getting incorrect Covid test results will cause positive cases to ripple through the community, but epidemiologists say Australia’s infection rate is now so high it might not make a significant difference.
Over the Christmas period St Vincent’s hospital told 886 people their result was negative, when in fact they were positive.
The hospital’s pathology department, SydPath, has apologised for the “specific human error” that led to the wrong results being delivered.
Initially 400 people were sent text messages saying they had a negative result, but were later told they were positive. Another 950 people were told they were negative when the results were not yet known, with 486 of them later told they were positive.
“Once again, we are sincerely sorry for this error and acknowledge the significant impact it has had on those involved,” SydPath said in a statement, adding that it had procedures in place to ensure it wouldn’t happen again.
Natasha Malani has been told she caught Covid from one of those mistakenly given the all clear, who then travelled to Adelaide and dined at the same restaurant she was in.
Malani, the chief executive of the business group South Australian Leaders, said four out of the group of six she dined with were now infected.
By the time she knew she was infectious, she had spent Christmas with her family, and had spent time with friends and colleagues.
“That person came to Adelaide thinking they were negative … then got a result saying ‘sorry, we made a mistake, it was positive’,” she said.
South Australia reported 1,471 new cases on Wednesday, a record for the state. The premier, Steven Marshall, said the Omicron variant was moving “too quickly”, and announced new restrictions on elective surgery and the scrapping of PCR tests for interstate travel due to a lack of capacity.
Single events have caused a large number of cases at different times in the pandemic, including many deaths before vaccines became available. More than 850 cases were linked to the Ruby Princess cruise ship after it docked in Sydney and let off 2,700 passengers in March 2020..
But experts say that with daily cases now past the 18,000 mark across Australia, the relative effect of hundreds of people unknowingly spreading Covid is small compared with the early days of the pandemic, even if that is small consolation for the individuals and families affected.
Deakin University’s chair of epidemiology, Prof Catherine Bennett, said the extent to which the error increased the number of cases would depend on how much people were moving around.
“It is an unfortunate time of year. Those who did change their behaviour did so because they thought they were cleared – so they went out,” she said.
“People were probably getting a test to clear themselves for Christmas. Some of them would have been in isolation anyway, some were in quarantine …
“Say a third of them went out and did the family thing, it probably has changed the risk for those families.”
But with thousands of positive cases every day, Bennett said, a few hundred wouldn’t make a large overall difference.
Mary-Louise McLaws, a University of NSW professor of epidemiology and adviser to the World Health Organization, said it was clear Christmas could be a super-spreader event.
“Authorities around the country have heard the potential worst-case scenario from multiple modellers [but] you don’t need models to tell you what could happen,” she said.
“It’s not unusual that Christmas is a super-spreader event.
“[The SydPath situation] would have the potential of another increase in case numbers. Once you’re given a negative test, at a highly sociable period of the year, they would have gone out immediately … the majority would be young adults going ‘woohoo, I’m negative, I can go and see my friends’.”
Michael Lydeamore, a lecturer in Monash University’s econometrics and business statistics department, said the flow-on effect would have made a difference as people travelled in the Christmas period while infectious.
But he said with so many cases of community transmission it would not make “as big a difference as people think”. Because authorities were no longer tracking “trees of transmission”, it was unlikely the true effect would ever be revealed.
