existing macroscopic epidemic models.[@daley2001epidemic] For example, the SI model describes the growth of infection rate as the product of the current infection rate and the current susceptible rate. The SIR model further incorporates the effect of recovery into the model, i.e., when the infected population turns into immune population after a certain period of time. The SIRS model considers the case that immunity is not for lifetime and that the immune population can become susceptible population again. In addition to these models, the SEIR model incorporates the incubation period into analysis. Incubation period refers to the duration before symptoms show up.[@yan2006seir] The most important factor in all those models is $R0$, the regeneration number, which tells how fast the disease can spread. $R0$ can be regressed from data.

#### Limitations of Existing Models

Although these models are useful in predicting the spread of epidemics, they lack the granularity needed for analyzing individual behaviors during an epidemic and understanding the relationship between individual decisions and the spread of the disease.[@barrett2009estimating] For example, many countries now announced “lock-down", “shelter-in-place", “stay-at-home", or similar orders. However, their effects are very different across different countries, or even across different counties in the same country. One 