Database Reference
In-Depth Information
1: CONTAGIOUS
2: IMMUNE
3: NON IMMUNE
4: SICK
1:
350000.00
2:
1980000.00
3:
1000000.00
4:
350000.00
2
2
1:
175000.00
2:
990000.00
3
2
2
3:
500000.00
4:
175000.00
3
3
3
1:
0.00
2:
0.00
3:
0.00
4
4
1
4
1
1
1
4
4:
0.00
0.00
75.00
150.00
225.00
300.00
Weeks
Fig. 2.2
Ensuing epidemics occur with regular frequency and are increasingly less severe,
finally reaching a steady-sized nonimmune population. (Can you explain why this is
so?) The disease has become endemic. At this steady state, the immune population is
growing at the birth rate, and the contagion rate is constant and equal to the birth rate.
BASIC MODEL
CONTAGIOUS(t)
=
CONTAGIOUS(t
−
dt)
+
(GET SICK
−
STAY IN BED) * dt
INIT CONTAGIOUS
=
1
{
Individuals
}
INFLOWS:
GET SICK
=
CONTACT RATE * (CONTAGIOUS
+
SICK) * NON IMMUNE
{
Individuals per Time Period
}
OUTFLOWS:
STAY IN BED
=
CONTAGIOUS
{
Individuals per Time Period
}
IMMUNE(t)
=
IMMUNE(t
−
dt)
+
(RECOVER) * dt
INIT IMMUNE
=
0
{
Individuals
}
INFLOWS:
RECOVER
=
.9*SICK
{
Individuals per Time Period
}
NON IMMUNE(t)
=
NON IMMUNE(t
−
dt)
+
(BIRTHS
−
GET SICK) * dt
INIT NON IMMUNE
=
1000000
{
Individuals
}
INFLOWS:
BIRTHS
=
5000
{
Individuals per Time Period
}
OUTFLOWS:
GET SICK
=
CONTACT RATE * (CONTAGIOUS
+
SICK) * NON IMMUNE
{
Individuals per Time Period
}
SICK(t)
=
SICK(t
−
dt)
+
(STAY IN BED
−
RECOVER
−
DIE) * dt
INIT SICK
=
0
{
Individuals
}
