When we used low, medium or high mean expression levels of Cathepsin B/L in our calculations (Fig 2H), with the TMPRSS2 expression level unaltered (Fig 2A), we found that the extent of infection increased in the absence of drugs from ~2960 cells/ml at low to ~5390 cells/ml at high Cathepsin B/L expression (Fig 2I). Here, CTSB is linked to infection.