COVID-19 is a highly contagious disease caused by the coronavirus SARS-CoV-2, which first emerged in Wuhan, China, in December 2019. The World Health Organization (WHO) declared it a global pandemic in March 2020, and finally ended the global health emergency in May 2023. Symptoms typically include fever, fatigue, cough, and loss of smell or taste, appearing 1–14 days after exposure; while most cases are mild, 14% become severe, 5% critical, and some suffer from long COVID. The virus spreads through airborne particles and contaminated surfaces, particularly indoors, and infected individuals can remain contagious for up to 20 days even without symptoms. Prevention relies on vaccination, masking, distancing, and handwashing, while treatment involves antiviral drugs and supportive care. Scientists believe the virus emerged through natural zoonosis, like previous outbreaks, and the WHO formally named the disease and virus on 11 February 2020.