COVID-19 disease overview: symptoms, transmission and prevention

COVID-19 is caused by the SARS‑CoV‑2 virus and spread worldwide beginning in early 2020. Typical symptoms include fever, fatigue, cough, shortness of breath, loss of smell and taste; about one‑third of infected people remain asymptomatic. Among those who develop illness, roughly 81 % experience mild or moderate disease, 14 % develop severe respiratory problems, and 5 % become critically ill with possible organ failure. Transmission occurs through respiratory droplets and aerosols, especially indoors, and the virus can remain contagious for up to 20 days. Diagnostic testing relies on RT‑PCR, transcription‑mediated amplification or RT‑LAMP of nasopharyngeal samples. Vaccines have been approved in many nations, and public health measures such as masking, social distancing, ventilation and hand hygiene remain essential to limit spread.