I once looked into the effectiveness of Australia and New Zealand’s quarantine programs to get a sense for this. I think, until recently, basically no infectious cases made it through their 2-week quarantines. Their track records have become more marred since Delta arrived.
For New Zealand, if I recall correctly, basically no community infection clusters were due to quarantine breakthroughs (citation needed!). Of the cases caught with PCR, 80% tested positive on day 3 of quarantine, and the remaining 20% were positive on day 12.
So while some cases might have not been detected, it seems like these didn’t go on to infect others after the 2 weeks. The people getting tested on day 3 could have been infected on their plane flight, or perhaps some days before their flight. I’d guess the median infection was a week old by day 3 of quarantine.
Anyhow, NZ’s numbers seemed to rule out a 50% false-negative rate, because I think their quarantine would have failed if so. They also seem to rule out a 2% false-negative rate, at least for tests done early after infection.
Our current Delta outbreaks are tracable to a limo driver who was not—nor required to be—vaccinated or even masked while transferring travellers from their flight to hotel quarantine.
The main source of our success has been in massively cuts to the number of travellers we allow in, and that has it’s own obvious problems...
In Australia, hotel quarantine has caused one outbreak per 204 infected travellers. Purpose-built facilities are far better, but we only have one (Howard Springs, near Darwin) and the federal government has to date refused to build any more.
But no cases of infections slipping thru the testing, no?
As far as I know none of our leaks have been by releasing an infectious person after a negative test result.
It’s possible for PCR tests to return negative for a very early (low viral load) infection though; that’s why for high-risk travellers we do PCR tests on days −3, 1, 5, 11, and 14 of the quarantine period. For low-risk settings, ie contact tracing, you only need to isolate until you get a negative PCR test result.
I once looked into the effectiveness of Australia and New Zealand’s quarantine programs to get a sense for this. I think, until recently, basically no infectious cases made it through their 2-week quarantines. Their track records have become more marred since Delta arrived.
For New Zealand, if I recall correctly, basically no community infection clusters were due to quarantine breakthroughs (citation needed!). Of the cases caught with PCR, 80% tested positive on day 3 of quarantine, and the remaining 20% were positive on day 12.
So while some cases might have not been detected, it seems like these didn’t go on to infect others after the 2 weeks. The people getting tested on day 3 could have been infected on their plane flight, or perhaps some days before their flight. I’d guess the median infection was a week old by day 3 of quarantine.
Anyhow, NZ’s numbers seemed to rule out a 50% false-negative rate, because I think their quarantine would have failed if so. They also seem to rule out a 2% false-negative rate, at least for tests done early after infection.
In Australia, hotel quarantine has caused one outbreak per 204 infected travellers. Purpose-built facilities are far better, but we only have one (Howard Springs, near Darwin) and the federal government has to date refused to build any more.
Our current Delta outbreaks are tracable to a limo driver who was not—nor required to be—vaccinated or even masked while transferring travellers from their flight to hotel quarantine.
The main source of our success has been in massively cuts to the number of travellers we allow in, and that has it’s own obvious problems...
But no cases of infections slipping thru the testing, no?
As far as I know none of our leaks have been by releasing an infectious person after a negative test result.
It’s possible for PCR tests to return negative for a very early (low viral load) infection though; that’s why for high-risk travellers we do PCR tests on days −3, 1, 5, 11, and 14 of the quarantine period. For low-risk settings, ie contact tracing, you only need to isolate until you get a negative PCR test result.