I have no idea if this has been posted before but here is a NIH study on the infectivity rate of the chinavirus.

chinavirus positive people where tasked to infect 455 non-positive healthy people and with the various ways to try and infect them shows not a single one of the 455 people got infected!

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7219423/

published 13th of may but is still relevant