On the basis of a compartment model, the epidemic curve is investigated when the net rate $\lambda$ of change of the number of infected individuals $I$ is given by an ellipse in the $\lambda$-$I$ plane which is supported in $[I_{\ell },I_h]$. With $a\equiv (I_h-I_{\ell })∕(I_h+I_{\ell })$, it is shown that (1) when $a<1$, oscillation of the infection curve is self-organized and the period of the oscillation is in proportion to the ratio of the difference $(I_h-I_{\ell })$ and the geometric mean $\sqrt{I_h{I}_{\ell }}$ of $I_h$ and $I_{\ell }$, (2) when $a=1$, the infection curve shows a critical behavior where it decays obeying a power law function with exponent $-2$ in the long time limit after a peak, and (3) when $a>1$, the infection curve decays exponentially in the long time limit after a peak. The present result indicates that the pandemic can be controlled by a measure which makes $I_{\ell }<0$.

在隔间模型的基础上，研究流行曲线时净率$\lambda$受感染人数的变化$我$由椭圆给出$\lambda$-$我$支持的平面$[{我}_{\ell },{我}_H]$. 和$\mathrm{一种}\equiv ({我}_H-{我}_{\ell })∕({我}_H+{我}_{\ell })$, 结果表明 (1) 当$\mathrm{一种}<\mathrm{1个}$，感染曲线的振荡是自组织的，振荡的周期与差异的比率成正比$({我}_H-{我}_{\ell })$和几何平均数$\sqrt{{我}_H{我}_{\ell }}$的${我}_H$和${我}_{\ell }$, (2) 当$\mathrm{一种}=\mathrm{1个}$，感染曲线显示出一种临界行为，它服从具有指数的幂律函数衰减$-\mathrm{2个}$在峰值后的长时间限制中，以及 (3) 当$\mathrm{一种}>\mathrm{1个}$，感染曲线在峰值后的长时间限制内呈指数衰减。目前的结果表明，可以通过采取以下措施来控制大流行${我}_{\ell }<0$.