A compartmental model for the analysis of SARS transmission patterns and outbreak control measures in China

Zhang, Juan; Lou, Jie; Ma, Zhien; Wu, Jianhong

We propose a compartmental model BloComp(2,7) that mimics the SARS control strategies implemented by the Chinese government after the middle of April 2003: the division of the whole population into two parallel blocks corresponding to the so-called free environment and the isolated environment and the partition of these blocks further into the compartments of susceptible, exposed, infective, possible, diagnosed, removed and the health care workers. We introduce a novel approach to calculate the transfer rate from the free environment to the isolated environment, and we incorporate into the model the fact that many individuals were misdiagnosed as SARS suspected and hence were mistakenly put in the isolated environment due to lack of fast and effective SARS diagnostic tests. We develop some methods for the parameter identification using the daily reported data from the Ministry of Health of China. Simulations based on these parameters agree with the accural data well, thus provide additional validation of the model. We then vary some parameters to assess the effectiveness of different control measures: these new parameters correspond to the situation when the quarantine measures in the free-environment were prematurely relaxed (we thus observe the second outbreak with the maximal number of daily SARS patients much higher than the first outbreak) or when the quarantine time of SARS patients is postponed (we observe delayed peak time but with much higher number of SARS patients at the peak). We also calculate the basic reproductive number and the basic adequate contact rate.