The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated disease, coronavirus disease 2019 (COVID-19), has caused a devastating pandemic worldwide. Here, we explain basic concepts underlying the transition from an epidemic to an endemic state, where a pathogen is stably maintained in a population. We discuss how the number of infections and the severity of disease change in the transition from the epidemic to the endemic phase and consider the implications of this transition in the context of COVID-19.

中文翻译：

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向地方性过渡：了解 COVID-19

严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 及其相关疾病 2019 冠状病毒病 (COVID-19) 的出现已在全球范围内造成毁灭性大流行。在这里，我们解释了从流行病到地方病状态转变的基本概念，在这种状态下，病原体在人群中稳定存在。我们讨论了感染数量和疾病的严重程度在从流行阶段过渡到地方流行阶段时如何变化，并考虑了这种过渡在 COVID-19 背景下的影响。