Surgical masks are not effective at preventing infection. They are effective at spreading infection.
New data on asymptomatic spreaders means than public health authorities are considering changing their advice. The default assumption would then be that everyone has it, and should therefore wear a mask to prevent spreading it.
> Laboratory tests find that improvised cloth masks block 60 – 80% of virus particles
How many virus particles do you need to become infected? Is 20% of the load in a typical aerosol droplet from an asymptomatic infected person above or below that critical number?
It's a numbers game. There is a certain probability that each virion can spur and infection, so the less you get the better. If virions had a 100% infection chance then sure, but it's much lower than that.
>Surgical masks are not effective at preventing infection.
Actually, they very much are.
1. Regular old surgical masks (not N95 respirators), when worn by the public without training, had a strong protective effect for the people wearing them during the SARS-CoV-1 outbreak. They reduced the risk of infection by ~70%. (Source: https://wwwnc.cdc.gov/eid/article/10/2/03-0730_article) The CDC even coauthored this one.
2. Despite being very different in their ability to actually filter out fine particles, N95 respirators and surgical masks actually show no significant difference in their ability to prevent diagnosed respiratory infections including influenza, when worn by healthcare workers according to two large meta-studies. Though both had a protective effect over no mask. (Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4868605/) (2nd source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/)
3. When infected people wear a mask, it does help reduce the amount of viral shedding which occurs, presumably making them less likely to infect others. (Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3591312/)
Surgical masks are not effective at preventing infection. They are effective at spreading infection.
New data on asymptomatic spreaders means than public health authorities are considering changing their advice. The default assumption would then be that everyone has it, and should therefore wear a mask to prevent spreading it.