The effect of control strategies that reduce social mixing on outcomes of the COVID-19 epidemic in Wuhan, China

Kiesha Prem; Yang Liu; Tim Russell; Adam J Kucharski; Rosalind M Eggo; Nicholas Davies; Mark Jit; Petra Klepac

We divide the population according to the infection status into susceptible ( ), exposed ( ), infected ( ), and removed ( ) individuals, and according to age into five-year bands until age 75 and a single category aged 80+ (resulting in the total of 16 age categories, ). Susceptible individuals may acquire the infection at a given rate when they come into contact with an infectious person, and enter the exposed disease state before they become infectious and later either recover or die. We assume Wuhan to be a close system with a constant population size of 11 million (i.e., = + + + = 11 million) throughout the course of this epidemic. We considered the SEIR model presented in Figure 1 . The agespecific mixing patterns of individuals in age group alter their likelihood of being exposed to the virus given a certain number of infectives in the population. In addition, we incorporated contributions of asymptomatic and subclinical cases, however, the question of whether they are able to transmit infection is still not resolved at the time of writing, although current evidence suggests that they are likely to. 19 We further considered a scenario where we assumed that younger individuals are more likely to be asymptomatic (or subclinical) and less infectious than older individuals. 20, 21 For a given age group , epidemic transitions can be described by: