We analyse the patterns of the current epidemic evolution in various countries with the help of a simple SIR model. We consider two main effects: climate induced seasonality and recruitment. The latter is introduced as a way to palliate for the absence of a spatial component in the SIR model. In our approach we mimic the spatial evolution of the epidemic through a gradual introduction of susceptible individuals.

We apply our model to the case of France and Australia and explain the appearance of two temporally well-separated epidemic waves. We examine also Brazil and the USA, which present patterns very different from those of the European countries. We show that with our model it is possible to reproduce the observed patterns in these two countries thanks to simple recruitment assumptions. Finally, in order to show the power of the recruitment approach, we simulate the case of the 1918 influenza epidemic reproducing successfully the, by now famous, three epidemic peaks.

我们借助一个简单的 SIR 模型分析了各国当前流行病演变的模式。我们考虑两个主要影响：气候引起的季节性和招聘。引入后者是为了缓解 SIR 模型中空间分量的缺失。在我们的方法中，我们通过逐步引入易感个体来模拟流行病的空间演变。

我们将我们的模型应用于法国和澳大利亚的案例，并解释了两个时间上分开的流行波的出现。我们还考察了巴西和美国，它们呈现出与欧洲国家截然不同的模式。我们表明，由于简单的招聘假设，我们的模型可以在这两个国家重现观察到的模式。最后，为了展示招募方法的威力，我们模拟了 1918 年流感流行成功复制了现在著名的三个流行高峰的案例。