More than 500 Canberrans have reported having COVID more than once

But officials have been quick to caution that this may not necessarily be a reinfection but rather a "second episode" of COVID-19. Officials say measuring reinfections is difficult.

The BA.5 subvariant of COVID-19 has also been detected in Canberra for the first time, in a sample collected from a recently returned overseas traveller.

The latest weekly report from ACT Health, which covers the week from May 2 to May 8, said 508 individuals had reported more than one episode of COVID-19 since March 2020.

The report said less than half - 45 per cent - had their first positive test in December 2021 or later.

"Currently, there is no national agreed case definition for a reinfection of COVID-19," the report said.

"It is expected that the risk of reinfection will increase over time as immunity wanes from infection and vaccination and new subvariants/variants emerge."

ACT Health said it had defined "multiple episodes" as a person who had an initial positive COVID-19 test and a subsequent positive test after the nationally recommended testing window current at the time of the test.

Chief health officer Kerryn Coleman said authorities had been working over the past couple of months on how reinfections could be measured.

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"It's not an easy thing to do with our data and I know lots of other jurisdictions have had a challenge with that as well," Dr Coleman told ABC radio.

"[There are about] 500 entries in our system of more than 100,000 which look like they are a second report. That doesn't necessarily mean they're a reinfection but it might mean that they're reporting a second episode of having another PCR or a [rapid antigen test] positive.

"That's incredibly tiny but we'll continue to have a look at the data, monitor what's happening in the rest of the nation as well as internationally."

Experts believe a COVID-19 reinfection surge is under way across Australia, but the true picture may never be known as governments abandon attempts to track second cases.

The ACT has recorded 1217 new COVID cases in the 24 hours until 8pm on Thursday. On Wednesday, there were 1132 new cases.

There are 74 people with the virus in hospital. Four patients are in the ICU and one is on a ventilator.

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