Fig. 1

Scheme plot of case transmission between the control zone and the social zone. The left panel (a) corresponds to Scenario (a) with a perfect isolation policy; the right panel (b) corresponds to Scenario (b) with an imperfect isolation policy. The blue arrow indicates that the cases are transferred from the social zone to the control zone due to epidemiological control. The red arrow represents the transmission direction, i.e., the individual indicated by the arrow is infected by the individual behind the arrow. The green color in the box means that the population number is known; the orange color means that the population number is not directly known. The black arrow refers to the inclusion relation of the case classification