We are living in times where a viral disease has brought normal life in much of the world to a halt. Named after its causative agent, coronavirus disease 2019 (COVID‐19) is caused by a novel coronavirus recently renamed as severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2).1 Coronavirus disease 2019 manifests as dry cough, frequent fevers and in severe cases pneumonia. Older patients and patients with underlying comorbidities are at a higher risk of death.2, 3 Until 11 March 2020, when the World Health Organization characterized the situation as a pandemic, there were 118 000 cases in 114 countries with 4291 deaths. It is the first pandemic caused by a coronavirus.4, 5

In such times, it would not be surprising if a lot of us were wondering, how something that is invisible even under a light microscope infects people and wreaks such a havoc. While we do not have all the answers yet, refreshing our basics and understanding the what, the why and the how of the virus would definitely help us better understand the situation.

我们生活在病毒性疾病导致世界大部分地区正常生活陷入停顿的时代。 2019 年冠状病毒病 (COVID-19) 以其病原体命名，是由一种新型冠状病毒引起的，最近更名为严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2)。 1 2019冠状病毒病表现为干咳、频繁发烧，严重时出现肺炎。老年患者和患有潜在合并症的患者死亡风险较高。 2, 3截至 2020 年 3 月 11 日，世界卫生组织将这种情况定性为大流行病，114 个国家已出现 118 000 例病例，4,291 人死亡。这是首次由冠状病毒引起的大流行。 4, 5

在这样的时代，如果我们很多人都想知道，即使在光学显微镜下也看不见的东西如何感染人类并造成如此严重的破坏，也就不足为奇了。虽然我们还没有找到所有的答案，但刷新我们的基础知识并了解病毒的本质、原因和方式肯定会帮助我们更好地了解情况。