The outbreak pattern of SARS cases in China as revealed by a mathematical model

Since it first appeared in China's Guangdong Province, Severe Acute Respiratory Syndrome (SARS) has caused serious damages to many parts of the world, especially Asia. Little is known about its epidemiology. We developed a modified discrete SIR model including susceptible individuals, non-hospitalized SARS persons; hospitalized patients, cured hospital patients, and those who have died due to SARS infection. Here, we demonstrate the effective reproduction number is determined by infection rates and infectious period of hospitalized and non-hospitalized SARS patients. Both infection rate and the effective reproductive number of the SARS virus are significantly negatively correlated with the total number of cumulative cases, indicating that the control measures implemented in China are effective, and the outbreak pattern of accumulative SARS cases in China is a logistic growth curve. We estimate the basic reproduction number R(0) of SARS virus is 2.87 in mainland of China, very close to the estimations in Singapore and Hong Kong.