BETA 1, BETA 2 1, and BETA 2. How are the results affected by the choice of
survival rates? How does the outbreak pattern of the disease change for smaller DT
and for different integration methods?
21.4 Two Infective Populations Model Equations
I_1(t) ¼ I_1(t À dt) + (CONTRACTION_1 À SURVIVE_1 À DIE_1) * dt
INIT I_1 ¼ 5
INFLOWS:
CONTRACTION_1 ¼ BETA_1 * S_1 * I_1 + BETA_1_2 * S_1 * I_2
OUTFLOWS:
SURVIVE_1 ¼ SURVIVAL_RATE_1 * I_1
DIE_1 ¼ (1ÀSURVIVAL_RATE_1) * I_1
I_2(t) ¼ I_2(t À dt) + (CONTRACTION_2 À DIE_2 À SURVIVE_2) * dt
INIT I_2 ¼ 20
INFLOWS:
CONTRACTION_2 ¼ RATE_OF_CONTACT_2 * I_2 * S_2
OUTFLOWS:
DIE_2 ¼ (1-SURVIVAL_RATE_2) * I_2
SURVIVE_2 ¼ SURVIVAL_RATE_2 * I_2
S_1(t) ¼ S_1(t À dt) + (NONIMMUNE_IMMIGRANTS_1 À CONTRACTION_1) * dt
INIT S_1 ¼ 1000
INFLOWS:
NONIMMUNE_IMMIGRANTS_1 ¼ 7
OUTFLOWS:
CONTRACTION_1 ¼ BETA_1 * S_1 * I_1 + BETA_1_2 * S_1 * I_2
S_2(t) ¼ S_2(t À dt) + (NONIMMUNE_IMMIGRANTS_2 À CONTRACTION_2) * dt
INIT S_2 ¼ 1000
INFLOWS:
NONIMMUNE_IMMIGRANTS_2 ¼ 10
OUTFLOWS:
CONTRACTION_2 ¼ BETA_2 * I_2 * S_2
BETA_1 ¼ .008
BETA_1_2 ¼ 0.00015
BETA_2 ¼ .003
SURVIVAL_RATE_1 ¼ .065
SURVIVAL_RATE_2 ¼ .2
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21 Infectious Diseases