It is obvious that people's movements are the cause of the COVID-19 outbreak. In this model, the movements of human agents were considered in two modes. They move either by their personal vehicles or public transportations. In this model, humans based on age were classified into four groups (Table 2 ): 5 and less, more than 5 to 24, more than 24 to 64, and more than 64. It was assumed that humans who are more than 24 years old (two last groups) can have personal vehicles, of which 63% were assumed to have personal vehicles according to the statistics of people having personal vehicles in Urmia city. It should be noted that the rest of humans were assumed to move by public transportations. On the other hand, humans based on the occupation were classified into four classes of civil servants, self-employed, students, and the rest of the people who are not in any of the first three classes. In this ABM, it was assumed that students were assigned to human agents who are more than 5 and less than 24 years old, and civil servants, as well as self-employed employees, were assigned to human agents who are more than 24 years old. Similarly, the number of human agents in each group was determined according to the statistics of human resources in Urmia city.
The selection of agents' workplaces was performed randomly among the office, business, or school cells on the basis of agents' occupations. During the simulation, for each human agent, a cell was assigned as the workplace and does not change. It should be noted that the same cell can be several human agents' workplaces since the selection of the workplaces was done randomly. In this model, all employees (civil servants and self-employed) and students move between their houses and workplaces twice a day. To simulate the movements of human agents, one day was divided into four time intervals: in the first time interval, employee agents (civil servants and self-employed) who have personal vehicles move from their houses to their workplaces by their own vehicles and in this time interval, there is not any risk of becoming infected for these human agents. On contrary, employee agents who do not have personal vehicles as well as student agents in order to move from their houses to their workplaces, use public transportations and in this case, they are likely to become exposed if there is any exposed human agent on their way to work regarding the R0  value of the exposed human agent as well as the COVID-19 transmission probability. It should be noted that the speed of public transportations with regard to their stops in stations was considered 45 km an hour and according to this speed, it was assumed that human agents move about 11.25 km every 15 min; therefore, the movements of human agents are updated every 15 min and their health status (see section 2.3.3) are investigated every 15 min based on the existence of exposed human agents in the same cells with them. It should be noted that in order to transmit the COVID-19 indoors, people should be kept at a distance of fewer than 2 m for at least 15 min; therefore, in this ABM, the time interval was considered 15 min and the dimension of the cells was taken into account 2 m. Human agents move between their houses and workplaces through road cells. All employees as well as students move to their own workplace cells in the second time interval and similarly, the probability of becoming exposed is investigated at their workplace cells. In the next time interval (the third time interval), employees and students come back from their workplaces to their houses in the same way described in the first time interval and the risk of disease transmission is investigated for employees who use public transportations as well as students; and in the last time interval, all employees and students move to their houses and in this time interval, the disease transmission is investigated among all members of the households. These processes are explicitly illustrated in Fig. 4 .
In our model, human agents at any moment of the simulation are in one of the susceptible, exposed, infected, recovered, or dead states and their states change regarding the SEIRD model. The states of human agents change under certain conditions over time. They will remain susceptible until they coincide with at least one exposed human agent in the same cells. In this case, based on the transmission probability as well as the R0 value of the exposed human agent, COVID-19 might be transmitted from an exposed human to a susceptible human. If the human agent becomes exposed, it starts to transmit the disease and this trend lasts 2-14 days (COVID-19 incubation period). After passing the incubation period which is considered diverse for each human agent, the state of exposed human turns into infected, and in this case, it will be quarantined. In the infected state, human agents cannot move and consequently spread the disease because of the quarantine. In the state of infected, one of two events regarding the age of the human agent happens: first, the infected human agent becomes recovered after 2-4 weeks, or second, the infected human agent dies. In Fig. 5 , the transition of states for human agents was shown.
In order to have an overview of the parameters of our ABM, input parameters of the model along with their values as well as the values assigned to the attributes of human agents were summarized in Table 3 . To initialize these values, previous studies and some of the most authoritative websites were used. For the parameters and attributes whose values were defined in a range, a normal distribution was considered. Moreover, for these parameters and attributes, the mean and standard deviation were also reported. It should be noted that the normal distribution was simply considered for these parameters and attributes due to the novelty of coronavirus as well as the lack of information on what distribution it follows (as a suggestion for future research, an investigation can be made on how these parameters (parameters defined in a range) are distributed; then, the values adjusted for these parameters would be based on the study of their changes in reality.).
In this research, all happened events concerned with the COVID-19 outbreak in the Urmia city along with their exact dates were considered in our ABM. In Iran, COVID-19 disease was transmitted from China to the city of Qom (the first city in Iran where COVID-19 was observed) and subsequently, from Qom to all cities in Iran. The first case of COVID-19 in the city of Urmia was identified on February 27. According to the official government news, this person had traveled to Qom and returned to Urmia on February 25; therefore, the beginning of our ABM was scheduled for February 25. In addition, one human agent was randomly considered exposed at the beginning of the ABM. Precede the outbreak of COVID-19 from Qom to all cities in Iran, the Iranian government in order to reduce the rate of COVID-19 outbreak closed all schools and educational centers on February 21. For this reason, at the beginning of our ABM, it was assumed that all student agents do not move in the ABM as well as about 30% of civil servant agents (those who are teachers in the real world). Similar to the first detected case, the second infected case with COVID-19 disease in the Urmia city was identified on March 2. This person also became infected due to traveling to Qom city and returned to Urmia city on February 28; so, another susceptible human agent was randomly selected among all human agents, and its health status was changed to exposed. In Iran, the New Year's holidays begin on March 18 and continue until March 23. During this period of time in the model, it is assumed that all human agents stayed at their houses and did not move to their workplaces or any other places. On March 27, the Iranian government in order to reduce the outbreak of the COVID-19 imposed the social distancing plan on the population. Regarding this event, only human agents who did not pay attention to social distancing were likely to become exposed. The interval between March 31 and April 1 was the official holidays of the New Year and similarly, all human agents were assumed to stay at their houses and there were not any human agents' movements in this interval in the model. It should be noted that in Iran, one day a week is a holiday and these holidays were also considered in the ABM according to the exact dates of them. Similar to other holidays, on these holidays, it was assumed that human agents stay in their houses and do not move. Fig. 6 clearly illustrates all that happened in the study area from the beginning of the epidemic to May 10 (the end of the simulation).