https://www.youtube.com/watch?v=cFB_C2ieW5I&t=12m50s * lots of secretions full of virus are worse than a little bit of secretions. more virus = person gets sicker * doctors might get coughed / sneezed at etc.

https://www.youtube.com/watch?v=cFB_C2ieW5I&t=15m50s (the same video) * N95 masks prevent things from getting in, surgical mask prevents things from getting out * N95 masks are in short supply

If I understand the expert correctly N95 are good and masks for everyone would be good, but there aren't enough for everyone.