We set difference equation madel about the varying of the number of diagnosing sufferers and suspect suffers;next,we discuss the number of diagnosing sufferer′s varying with date in different stage by solving the equation and assumption in reason,moreover,we simulate the epidemic situation of Beijing(2003.

To investigate the relationship between the epidemiological contact history and the levels of IgG antibodies of patients with SARS in order to evaluate the significance of contact history in the clinical diagnosis of this illness,302 probable cases with clinically diagnosed SAES were subjected to study by retrospective analysis of the contact history and the results of IgG testing.