Table 1 Model population definitions and initial values denoted with subscript 0 for each state variable.

Symbols	Initial values	Units	Definitions	Sources
S₀	Varies by country	People	Susceptible individuals	Vary
E₀	\({\mathcal{R}}_{0}\) · (I_A0 + I_S0)	People	Exposed individuals	Deduced
I_A0	I_S0	People	Asymptomatic individuals	Deduced
I_S0	Varies	People	Symptomatic individuals	Deduced
Rec₀	0	People	Recovered individuals	Deduced
W₀	1%	Unitless	% of viruses in environment	Deduced

Here we present definitions for the population groups represented by each compartment as well as their initial values. The initial value of the S and I_S populations vary by country, as shown in Table 2. We take the initial value of the I_A population to be the same as the initial value of symptomatic individuals as a conservative estimate. The initial value of the E population is computed by assuming that all initially-infected people (I_A0 + I_S0) have exposed the virus to approximately other people.
\({\mathcal{R}}_{0}\) (≈ 2.5).

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