the number of deaths during a particular period above the usual, expected number under normal conditions, which can show the effect of something like a disease or harmful event

We should develop methods to rapidly assess total excess mortality after natural disasters. 我们应该制定方法，迅速评估自然灾害后的总超额死亡率。

They analysed excess mortality from the Coronavirus (Covid-19) pandemic. 他们分析了冠状病毒（Covid-19）大流行期间的超额死亡率。