SARS疫情分析及对北京疫情走势的预测

在考虑每个SARS病人每日平均传染概率和他的直接传染的平均期限的基础上，建立了一个统计分析模型．分析表明，每个病人可以造成直接感染他人的期限平均在20天左右，这个值在不同地区和不同疫情阶段似乎变化不大．病人的平均每天感染率与社会状况有关，在疫情爆发期较大，在疫情控制期要小很多．北京后期如果控制在香港后期的感染率水平上，则有望在6月上中旬下降到日增几例．然后再经过约一个月，即7月上中旬达到日增0病例，而累积总病例数将达到3100多．但如果北京的新病例下降速度与广东类似的话，则要再多花至少一个月，才能达到上述的效果，且累积总病例数会达到3800左右．

Analysis of the current SARS epidemic and the forecast for Beijing

We set up a statistical analysis model by taking into account the average duration of the direct contagion of a SARS case and its average contagion probability per day. The calculation shows that the average duration of the direct contagion is about 20 days, which is not sensitive to the place and phase of the epidemic. On the other hand, the average contagion probability varies with social conditions. The probability is high in the initial phase but changes to a significantly smaller value in the controlled phase. If during the last phase the strictness of control in Beijing is comparable to that of Hong Kong in the corresponding phase, the number of new SARS cases may abate to a few per day in the first half of June and down to zero in mid\|July, with the accumulated total more than 3100. If the control strength is comparable to that of Guangdong in the corresponding phase, it will take at least one more month to reach the above performance and the accumulated total will be about 3800.