COVID-19 Overview: Symptoms, Transmission and Prevention

COVID-19 is a contagious disease caused by the SARS‑CoV‑2 virus, which spread worldwide from January 2020, leading to a global pandemic. Common symptoms include fever, fatigue, cough, breathing difficulty, loss of smell and taste; about one‑third of infections are asymptomatic. Among those who develop symptoms, roughly 81% experience mild to moderate illness, 14% develop severe disease with dyspnea or extensive lung involvement, and 5% become critically ill with respiratory failure or multiorgan dysfunction. Older adults face higher risk of severe outcomes, and many survivors report prolonged effects known as long COVID.

Transmission occurs primarily through inhalation of infectious particles or contact with eyes, nose, or mouth, especially in close indoor settings. People can remain contagious for up to 20 days, even without symptoms. Diagnostic testing relies on nucleic‑acid detection methods such as real‑time RT‑PCR, transcription‑mediated amplification and RT‑LAMP from nasopharyngeal swabs. Vaccines have been approved and are being distributed globally, complementing preventive measures like physical distancing, mask use, ventilation, hand hygiene and isolation of cases.