TABLE 3.

QMRA parameters for SARS-CoV-2 viral transmission^a

Parameter	Units	Description	Input valuesb	Distribution	References
Log10(Cvirus)	PFU·mL−1	Concn of virus in saliva	6.80 (6.10, 7.40)	Triangular	79, 103
FC	Cough·h−1	Coughing rate per hour	24.7 (10.0, 39.3)	Uniform	104
Handsa	m2	Surface area of two palms	1.8 × 10−2 (1.5 × 10−2, 2.2 × 10−2)	Triangular	105, 106
λhand	min−1	Viral decay on hand surface	1.20 (0.92, 1.47)	Uniform	107
Freq.hs	Contact·min−1	Contact frequency between hands and fomite	8.4 (5.4, 11.4)	Triangular	108
Freq.hf	Contact·min−1	Contact frequency between hands and face	0.261 (0.072, 0.450)	Triangular	109
F 23	Proportion	Proportion of virus transferred from hand to face	0.200 (0.063)	Normal	110
L dep	Proportion	Deposition fraction of virus into the lungs	1.00	Point	Assumed
I R	m3·h−1	Inhalation rate per hour	2.40 (1.62, 3.18)	Uniform	111
k risk c	PFU−1	Dose-response parameter to determine infection risk at a given viral dose	6.80 × 10−3	Point	80

^aQMRA, quantitative microbial risk assessment; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

^bThe values presented as mode (minimum, maximum) for triangular distributions, mean (minimum, maximum) for uniform distributions, and mean (SD) for normal distributions.

^cThis upper estimate, within the published k_risk range (80), was used to calibrate our model to documented SARS-CoV-2 outbreaks, as described in the materials and methods.