Table 1. An extended definition for the transmission rate (β) is the number of persons infected per infectious person per day while the basic reproductive number (R₀) is the average number of secondary cases an infectious individual can generate when this rate is introduced into a susceptible population.

Parameter	Definition	Baseline value
pa	Reduction in risk of infection for class S2	0.33
ρa	Initial proportion of the population at higher risk for SARS	0.77
βb	Transmission rate per day	0.25
1/ka	Mean incubation period (days)	6.37
1/γ1	Mean infectious period (days)	28.4
1/γ2a	Mean infectious period for persons with diagnosed SARS (days)	23.5
1/α	Mean period before diagnosis (days)	4.85
δa	Induced death rate per day	0.0279
q	Relative measure of infectiousness for the exposed class	0.1
l c	Relative infectiousness after isolation has begun	[0,1]

^aBaseline values for k, γ₂, α, ρ, p and δ have been taken from reference 3.
^bβ = 0.25 is our estimated transmission rate in Hong Kong.
^cl = 0 means perfect isolation, while l = 1 means no isolation.