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?
There is no evidence of asymptomatic spread what so ever. The study was conducted on 10 million people.
No evidence of asymptomatic spread in a study of 10 million
No evidence of asymptomatic spread in a study of 10 million
There's some (people like to pick and choose papers purely to only show their viewpoint as above...) but its a lot less than symptomatic.
https://www.bmj.com/content/371/bmj.m4851
The transmission rates to contacts within a specific group (secondary attack rate) may be 3-25 times lower for people who are asymptomatic than for those with symptoms.
doi:10.1371/journal.pmed.1003346 pmid:32960881
https://www.medrxiv.org/content/10.1101/2020.09.01.20135194v2
doi:10.1001/jamanetworkopen.2020.31756 pmid:33315116
doi:10.1371/journal.pone.0240205 pmid:33031427
This study ( https://doi.org/10.1101/2020.11.04.20225573 ) put the risk at 25%
This meta study ( https://doi.org/10.3138/jammi-2020-0030 (2020) ) found 17%
https://doi.org/10.1016/S0140-6736(20)32651-9 found roughly 20%.
So there's quite a bit of data suggesting it does exist (as we'd expect it to as other related diseases do) but it looks to be only 25% or lower in infectivity.
A few things though. Although its often quoted 33% are asymptomatic, we don't actually have reliable data on the % of asymtpomatic.
Not every PCR positive is actually infected so therefore not every PCR positive with no symptoms is actually asymptomatically infected.
We simply dont know the number.
An important one though is *pre* symptomatic transmission. These will have no symptoms YET but a relatively high viral load just prior to getting sick.
In my view this is the dangerous group, yes they'll get symptoms in a few days BUT would have spent several days infecting people before that.
If screening can catch these people it'll be a great help.
