The symptoms of COVID‑19 are variable but often include fever,[7] cough, headache,[8] fatigue, breathing difficulties, loss of smell, and loss of taste.[9][10][11] 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.[12][13] Of those who develop symptoms noticeable enough to be classified as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction).[14] Older people are at a higher risk of developing severe symptoms. Some people continue to experience a range of effects (long COVID) for years after infection, and damage to organs has been observed.[15] Multi-year studies are underway to further investigate the long-term effects of the disease.[16]