Background
Methods
Model
Event | Transition | Transition |
---|---|---|
during Δt
| rate | |
Infection of a |
S
s
→S
s−1
| |
susceptible in S
s
| ||
Infection of a |
S
p
→S
p
−1 | |
susceptible in S
p
| ||
Increase in exposed |
E
s
→E
s
+ 1 | |
class E
s
| ||
Increase in exposed |
E
p
→E
p
+ 1 | |
class E
p
| ||
Decrease in exposed |
E
s
→E
s
−1 |
γ
s
E
s
Δt + o(Δt) |
class E
s
| ||
Decrease in exposed |
E
p
→E
p
−1 |
γ
s
E
p
Δt + o(Δt) |
class E
p
| ||
Increase in asymptomatic |
A
s
→A
s
+ 1 | (1−p
s
)γ
s
E
s
Δt + o(Δt) |
infection A
s
| ||
Increase in asymptomatic |
A
p
→A
p
+ 1 | (1−p
p
)γ
p
E
p
Δt + o(Δt) |
infection A
p
| ||
Recovery from asymptomatic |
A
s
→A
s
−1 |
α
s
A
s
Δt + o(Δt) |
infection A
s
| ||
Recovery from asymptomatic |
A
p
→A
p
−1 |
α
p
A
p
Δt + o(Δt) |
infection A
p
| ||
Increase in symptomatic |
I
s
→I
s
+ 1 |
p
s
γ
s
E
s
Δt + o(Δt) |
infection I
s
| ||
Increase in symptomatic |
I
p
→I
p
+ 1 |
p
p
γ
p
E
p
Δt + o(Δt) |
infection I
p
| ||
Recovery from symptomatic |
I
s
→I
s−1
|
α
s
I
s
Δt + o(Δt) |
infection I
s
| ||
Recovery from symptomatic | ||
infection I
p
|
Parameterization of the model
Parameter | Description | Baseline values | Reference |
---|---|---|---|
R
0
| Basic reproduction number | 1.4 (range: 1.25−1.8) | |
δ
p
| Reduction in susceptibility of S
p
| 0−1 (0.48 in simulations) | [11] |
δ
a
| Reduction in transmissibility of A
s
and A
p
| 0.5 | [25] |
p
s
| Fraction of E
s
that become symptomatic | 0.6 | |
p
p
| Fraction of E
p
that become symptomatic | 0.3 | Assumption |
1/γ
s
| Exposed period of E
s
| 1.5 (days)−1
| [27] |
1/γ
p
| Exposed period of E
p
| 1.5, 2.6, 4.3, 6 (days)−1
| [10] |
1/α
s
| Infectious period of I
s
and A
s
| 5 (days)−1
| |
1/α
p
| Infectious period of I
p
and A
p
| varied in simulations | [10] |
β
| Baseline transmission rate | variable | Estimated from R
0
|
expression in (3) |