Coronavirus disease 2019 is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2. The first known case was identified in Wuhan, China, in December 2019. The disease quickly spread worldwide, resulting in the COVID-19 pandemic. Symptoms of COVID‑19 are variable, but often include fever, cough, headache, fatigue, breathing difficulties, loss of smell, and loss of taste. Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms. Of those people who develop symptoms noticeable enough to be classed as patients, most develop mild to moderate symptoms, while 14% develop severe symptoms, and 5% develop critical symptoms. Older people are at a higher risk of developing severe symptoms. Some people continue to experience a range of effects for months after recovery, and damage to organs has been observed.