14 days is the incubation period for COVID , the period after which we can be certain a person has not contracted he virus after exposure to it. The 10 days period is the time that is deemed for a person with COVID to be contagious after contracting it. They are different things
it was explained by the NSW CHO today as reported below in the Age
Why can COVID-19 cases be released from isolation after 10 days? A short explainer
By Natassia Chrysanthos
There has been some concern and confusion since
this morning's revelationthat a positive COVID-19 case was released from isolation in Victoria after just 10 days, and without a negative test.
NSW Chief Health Officer Kerry Chant has explained why that was the case. Essentially, a 14-day quarantine period applies to people who may have been exposed to the virus (such as close contacts or returned travellers) because that is the general incubation period for infection to reveal itself.
But when someone actually has COVID-19, a different isolation requirement sets in. The guidelines were established by the Communicable Diseases Network Australia, and they change depending on whether the person had a mild or serious case.
The returned traveller reported this morning, who first arrived in Victoria and travelled to Queensland, had a mild case of COVID-19. Dr Chant explained what rules applied and why:
"The guidelines require that you have 10 days in isolation after your [COVID-19] symptoms. So you flip from quarantining 14 days to [minimum 10 days] when you are a case.
"For mild cases you were able to be discharged if you were 10 days from your symptom onset and you had been free of symptoms for 72 hours before.
"The reason that was necessary is that we found cases where you can detect the virus in people's noses and throats, three months and even four months after the infection. What we're also observing is sometimes they may be negative at a certain point, but then you get a runny nose or something, and then if you get tested at that time, you can sometimes have the remnants of the virus come out.
"Because of that, you would have people permanently locked up. That's why the Communicable Disease Network looked at the evidence. That was that people are most infectious in that beginning bit, the pre-symptomatic time-frame."
That explains why some people can be released after 10 days so long as they have been free of symptoms for 72 hours. It also explains why a negative test was not required before cases left isolation and entered the community - a positive test at that later stage does not necessarily mean they are still infectious.
"Obviously there is a different set of criteria if you have been hospitalised, there are much more stringent guidelines," Dr Chant said. That different set of criteria also applies to people who were in intensive care or have had more intensive lung involvement.
Of course, these requirements have now shifted in light of the new mutant strains appearing overseas and arriving on Australian shores. "The Communicable Diseases Network Australia guidelines have been renewed and we will further discuss that situation today," Dr Chant said.
But in short: the minimum isolation period for positive mild cases has been lengthened to 14 days and a negative test will be required before people enter the community. Those who still test positive after their symptoms have passed will be assessed on a case-by-case basis.
"In NSW we've now re-instituted PCR testing on all negatives, but we are also making sure that we have the timely genetic genome sequencing, so again that can inform the decision-making," Dr Chant said.
"If you are negative, you will be able to [leave isolation], but we will extend the period to 14 days, not 10 days, as a precaution. We will test you before you go out and if you're negative, we will let you go out.
"If you are positive, we have a case-by-case assessment with experts who will do things like [assess] whether you have antibodies in response, whether the PCR marker is showing whether you're infectious," she said.
Such measures will alter the way that mild COVID-19 cases, such as the woman who travelled to Queensland from Victoria, will be treated in the future.
