Thanks. To how does it seem to fit with the logic and/or medical or public health "desirability" of testing asymptomatic people?

Thanks. To how does it seem to fit with the logic and/or medical or public health "desirability" of testing asymptomatic people?

Depends....

See the distinction above about pre-symptomatic v asymptomatic.

Pre-symptomatic will show no symptoms for 2-3 days after they become infectious and these have been shown to be as infectious as fully symptomatic.
Catching these people would obviously be beneficial.
So "asymptomatic testing" would include both groups.

The number of people truly asymptomatic isnt known with any real certainty. UK gov seems to be using roughly 1 in 3 but in reality depending on study this has been anything from 10% to 90%. Most likely this is due to PCR flagging people who arent infected at all as positive, these arent sick so classed as "asymptomatic".
Its a mess data wise.

While disease levels are high such as now, asymptomatic is likely such a low driver its not significant.
However, during low prevalence times such as last and next summer it might become more of a transmission driver in relative terms.
If you assume 1 in 3 are asymptomatic and each one of those has 20% or so as infectious as a symptomatic person then you can see there are enough people around undetected to keep community spread around.

So i can see the *logic* in testing for this (especially to get pre-symptomatic before they infect too many others) but in reality we're still utterly hamstrung by lacking a test that can actually flag infection as opposed to simply exposed so this cant really be done with any degree of accuracy.
We certainly shouldn't be diagnosing anyone at all as positive on the basis of 1 testing episode.

I've been losing track of this recently. Is anyone willing and kind enough to summarise for us non-medics what the current facts/evidence are?

The idea of the asymptomatic is an exciting gift to the fear and rumour mongers, since invisible or tiny evils are always a bit higher on the terror scale, e.g. poison gas, radioactivity, scorpions, black widows and so on. An invisible evil which can sneak up on you and whoosh, you're dead before you even saw it. Well that is scary. And I think the fear and rumour mongers have worked up the threat of asymptomatic spreaders with stressful consequences.

I'm tempted to call the whole idea a hoax, useful to drunk Fleet Street hacks to write a few hundred words on modern Typhoid Marys between lunch and going home time. A load of old rubbish.

You might be tempted to call it a hoax....

But there are a significant number of peer reviewed studies showing its happening to a degree.

Its also very common for many other viral diseases including the other HCoVs and influenza so it'd be more unusual if it WASNT happening.

Pre-symptomatic who are highly infectious are also grouped with "asymptomatic" in that they show no symptoms at the time of testing.

Thanks. To how does it seem to fit with the logic and/or medical or public health "desirability" of testing asymptomatic people?

Depends....

See the distinction above about pre-symptomatic v asymptomatic.

Pre-symptomatic will show no symptoms for 2-3 days after they become infectious and these have been shown to be as infectious as fully symptomatic.
Catching these people would obviously be beneficial.
So "asymptomatic testing" would include both groups.

The number of people truly asymptomatic isnt known with any real certainty. UK gov seems to be using roughly 1 in 3 but in reality depending on study this has been anything from 10% to 90%. Most likely this is due to PCR flagging people who arent infected at all as positive, these arent sick so classed as "asymptomatic".
Its a mess data wise.

While disease levels are high such as now, asymptomatic is likely such a low driver its not significant.
However, during low prevalence times such as last and next summer it might become more of a transmission driver in relative terms.
If you assume 1 in 3 are asymptomatic and each one of those has 20% or so as infectious as a symptomatic person then you can see there are enough people around undetected to keep community spread around.

So i can see the *logic* in testing for this (especially to get pre-symptomatic before they infect too many others) but in reality we're still utterly hamstrung by lacking a test that can actually flag infection as opposed to simply exposed so this cant really be done with any degree of accuracy.
We certainly shouldn't be diagnosing anyone at all as positive on the basis of 1 testing episode.

Thanks! That's very clear Splatt. The question remains I suppose is how much noise (and policy) is being generated by using 1 testing episode which could pick up both truly asymptomatic as well as pre-symptomatic.