For those without the uptake of preventive strategy, we developed a multi-state stochastic process to simulate the temporal natural course of cervical cancer from normal, cervical intraepithelial neoplasia (CIN) grade 1, CIN grade 2 or 3, local cancer and invasive cancer by the stratification of HPV infection (Fig. 1). The transition can only jump one state in one cycle (in year) whereas the regressions from HPV infection to no infection, CIN 1 without HPV infection to healthy, CIN 1 with HPV infection to HPV