COVID-19

新型冠状病毒感染

Evidence-backed information EN 5/7 applicable sections · ZH 5/7 applicable sections Updated Oct 23, 2026

COVID-19 is a contagious disease caused by the coronavirus SARS-CoV-2 that spread worldwide beginning in January 2020, leading to a global pandemic and a World Health Organization emergency declaration in March 2020, later ended in May 2023 ^[1]. Public-health measures such as social distancing were applied to slow transmission by reducing close contact ^[1]. The health effects of infection are prolonged in a substantial proportion of cases, imposing ongoing stress on health systems ^[2].

Read the full clinical and epidemiological profile 6

Definition

COVID-19 is a contagious disease caused by the coronavirus SARS-CoV-2 ^[1]. It emerged in January 2020 and spread worldwide, resulting in a pandemic and a declared global health emergency ^[1].

Clinical features

Symptoms of COVID-19 are variable but often include fever, fatigue, cough, shortness of breath, and loss of smell or taste ^[1]. They may appear one to fourteen days after exposure, and at least one third of infected persons remain without noticeable symptoms ^[1]. Among symptomatic patients, most have mild to moderate illness, while a minority develop severe or critical disease; older individuals face higher risk of severe outcomes ^[1]. Persistent symptoms lasting months or years, including fatigue and cognitive issues, occur in some people ^[1].

Epidemiology

The disease spread globally from January 2020, causing a worldwide pandemic and a WHO-declared emergency lasting until May 2023 ^[1]. Outbreaks occurred in prisons in 2020 owing to crowding and inability to enforce distancing ^[1]. A meta-analysis estimated a global pooled prevalence of post-COVID-19 condition at 28 or more days after infection of 0.43, with higher estimates among hospitalized patients and variation by region ^[2].

Transmission

COVID-19 is transmitted when infectious particles are inhaled or contact the eyes, nose, or mouth, with highest risk during close contact but also via suspended airborne particles indoors ^[1]. Transmission can occur after touching contaminated surfaces or objects and then touching the face ^[1]. Social distancing aims to slow spread by minimizing close interpersonal contact ^[1].

Prevention

Infection control through social distancing seeks to slow disease spread by reducing close contact between individuals ^[1]. Methods include quarantines, travel restrictions, and closure of congregate settings such as schools and workplaces, alongside individual actions like staying home, limiting travel, and avoiding crowded areas ^[1].

References

1 Wikipedia contributors. COVID-19 - Wikipedia [Internet]. Wikipedia. cited 3 Sept 2026. Available from: https://en.wikipedia.org/wiki/COVID-19
2 Chen C et al. Global Prevalence of Post-Coronavirus Disease 2019 (COVID-19) Condition or Long COVID: A Meta-Analysis and Systematic Review. J Infect Dis. 2022 Nov 1. PMID: 35429399. doi: 10.1093/infdis/jiac136. PubMed: https://pubmed.ncbi.nlm.nih.gov/35429399/