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Modern Geomatics Technologies and Applications

Fig. 2. States of human agents and the way human agents pass through them in the SEIRS model.

2.3.3. Calculation of malaria transmission in cells: In our model, the transmission of malaria parasite between human and
mosquito agents is possible only in two cases: (i) from infected humans to susceptible mosquitoes, and (ii) from infected
mosquitoes to susceptible humans. In the first case (i.e., when the infected human agent and the susceptible mosquito agent are
situated in the same cell), it is 2% likely that the malaria parasite will be transmitted from the infected human agent to the
susceptible mosquito agent [9]. In the event of happening this, the mosquito agent will be exposed. It takes approximately 10 to
21 days for the exposed mosquito to become infected [20]. Besides, mosquito agents remain infected for the rest of their lives if
they become infected. The second case happens when the susceptible human agent and the infected mosquito agent are situated
in the same cell. In this case, the cell calculates the probability of becoming exposed of the human agent, and if there is a chance
of infection, the human agent will be exposed. In order to calculate the probability of becoming exposed of human agents, firstly,
the risk value in each cell is calculated based on the reclassified values of cell’s attributes as well as the weights assigned to
environmental factors (i.e., these weights were calculated based on the analytic hierarchy process (AHP)), according to the index
overlay (IO) model (Eq. 1); then, the risk value obtained from Eq. (1) was normalized (i.e., the normalized risk value in each cell
indicates the probability of becoming exposed of human agents in that cell).

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_ = ∑( ∗ ) (1)

=1
Here, indicates the weight of the kth factor, indicates the reclassified value of the cell’s attribute corresponded to

the kth factor, and k is the number of the factor.
It should be noted that the weights assigned to environmental factors of air temperature, relative humidity, vegetation,
altitude, and distance from water sources were obtained 0.428, 0.274, 0.066, 0.174, and 0.058, respectively.

2.3.4. Assumptions considered in the proposed agent-based model: Generally, in simulation systems, the more parameters
used, the more accurate the results can be. In the meantime, using more criteria and parameters causes to complicate the model
as well as make it difficult to understand the content of the system; therefore, in order to avoid of the complexity of the model
as well as the deviation of our model from the defined aims, several assumptions were considered as follows:

 The human population was assumed to be constant.
 Each human agent was considered one person in the real world.
 Humans are considered as the only host of mosquito agents for feeding blood.
 The number of infected human agents at the beginning of the simulation was considered equal to the number of
malaria cases in December 2012 (i.e., four malaria cases). Besides, the rest of human agents were considered in the
susceptible state.
 Mosquito agents were assumed to lay eggs with equal proportions of males and females.
 Only permanent rivers in Saravan county were considered as suitable places for mosquitoes to lay eggs.
 Each day was considered as the time step of our simulation and the model was simulated for one year (the year 2013).

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