Yes, longer exposure time increases infection probability, but the 15 min threshold is arbitrary, like the 2 meter social distancing.
A bit like the "you can pick up food from the floor if it sat there for less than 5 seconds" meme.
Arbitrary guidelines are chosen:
- Because at the population level they're likely to be effective. Yes, individuals may get sick. Or die. But with the measures in place, overall risk and impacts should be reduced.
- They're actionable, memorable, and can be monitored and observed. Masking, hand-washing, limited exposures, limited occupancy, maintaining distance --- these all help reduce transmission, they're simple guidelines most people, even young children, should be able to comply with, and they can be readily and visibly observed.
It's a balance of benefits, risks, adoption, and enforcement.
Immunity status is harder to assure and measure, but vaccination standardises the innoculation, creates a memorialisable event, and can be checked if needed at specific locations and junctures.
The "five second rule" is far less meaningful than what's on the floor. But if you happen to see something fall, note that where it landed was reasonably clean, and if possible can wash it ... you're likely to make a better assessment than if it's been sitting for a few days. Even then, I'd make a sharp distinction between five seconds on my bedroom floor, vs. in the bath, or in a public building or street.
That said, much food comes from the ground. Wash and prepare suitably, you're reasonably safe.
One of the infections was traced to a department store and the interaction between the two people was caught on cctv. They walked past each other and didn't talk. It was seconds.
* A vast majority of infections can be traced
* You have an infection whose only traceable contact is for a few seconds in a store...
It seems pretty likely that the infection happened in the moments surrounding those few seconds. Especially when we have multiple circumstances like this. Especially when it agrees with our underlying understanding of the germ theory of disease.
Extended contact makes infection much more likely. But people who are sick shed live virus, and there's not a safe level of exposure of live virus where infection is impossible.
This becomes an unlikely explanation once
> > * A vast majority of infections can be traced
and
> > Especially when we have multiple circumstances like this.
The probability of an alternate explanation becomes exceptionally unlikely. It's further reduced by our general scientific understanding that:
> > But people who are sick shed live virus, and there's not a safe level of exposure of live virus where infection is impossible.
Infection from a momentary contact is fairly unlikely. But when you have a massive number of momentary contacts in the populace, it happening many times becomes a near certainty.
E.g., this:
> Several individuals in Australia were also infected with the Kappa variant through lingering virus aerosol particles in the hallway of a quarantine hotel in May. Though the individuals had no direct contact with each other they opened the doors to their hotel rooms within 30 minutes of each other and tested positive for the same strain.
No complete sequencing, but the same variant... spread several times apparently by the same mechanism of indirect contact, several individuals infected. In a quarantine hotel, where there's not many alternate explanations available.
Or this one, confirmed by sequencing:
> A similar event occurred earlier in April where two families quarantining in rooms next to one another were found to share the same viral sequence, after briefly opening their doors 30 minutes apart.
https://www.forbes.com/sites/williamhaseltine/2021/06/28/inf...
Source: https://www.abc.net.au/news/2021-06-22/covid19-cctv-footage-...
Were these single-digit infections all symptomatic, or were they detecting asymptomatic infections too? What is the false positive and false negative rate of the type of testing Australia is doing, and how many people were being tested during this time?
If some of the infections were asymptomatic, is it possible that some of them are false positives, and the fleeting encounter was also a false positive (either a false positive test, or that wasn't the true source of the infection) just due to random chance?
In answer to your final question - no - they were PCR confirmed cases. There was also a high degree of sequencing occurring to enable clarity on lineage transmission
In that period 30k-60k people where being tested in NSW. https://www.covid19data.com.au/nsw