Table 2.

Fraction, F_v, of free virus in lung mucus calculated by difference equation approach for range of virion to mucin molecule ratios representing exposure of virion to mucins at the aerosol particle/mucus interface.

Scenario 1: Number of virions to number of mucin molecules in 1 mm3 volume of mucus	Scenario 2: Number of virions to number of mucin molecules (volume of mucus)	Local ratio virion:mucin at aerosol particle/mucus interface	Fv at K mucin = 1010 M−1 (Reduction in risk by mucus)	Fv at K mucin = 1022 M−1.
1.42 × 1011 virions to 7.1 × 1010 mucins	7.1 × 1010 virions to 3.55 × 1010 mucins in 0.5 mm3.	2:1	0.5004 (2-fold)	*0.5000
1.07 × 1011 virions to 7.1 × 1010 mucins	7.1 × 1010 virions to 4.73 × 1010 mucins in 0.666 mm3.	1.5:1	0.334 (3-fold)	*0.333
7.1 × 1010 virions to 7.1 × 1010 mucins	7.1 × 1010 virions to 7.1 × 1010 mucins in 1 mm3.	1:1	0.0286 (35-fold)	0.3 × 10−7
3.55 × 1010 virions to 7.1 × 1010 mucins	7.1 × 1010 virions to 1.42 × 1011 mucins in 2 mm3.	1:2	0.00169 (588-fold)	1.4 × 10−11
<0.71 × 1010 virions to 7.1 × 1010 mucins	7.1 × 1010 virions to >7.1 × 1011 mucins in >10 mm3.	<0.1:1 (Eq. 8)	0.00085 (1,176-fold)	<10−15

*limit of what is achievable given ratio