COVID-19: Symptoms, transmission and prevention overview

COVID-19 is a contagious disease caused by the SARS‑CoV‑2 coronavirus. The outbreak began spreading worldwide in January 2020, leading to a global pandemic. Typical symptoms include fever, fatigue, cough, breathing difficulty, loss of smell and taste, with about one‑third of infections remaining asymptomatic. Among those who develop illness, roughly 81 % experience mild to moderate disease, 14 % develop severe respiratory problems, and 5 % become critical, potentially resulting in respiratory failure or multi‑organ dysfunction. Older adults are at higher risk, and some patients suffer lasting effects known as long COVID.

Transmission occurs through inhalation of infectious particles or contact with eyes, nose or mouth, especially in close indoor settings; the virus can remain airborne for extended periods. Infected individuals may stay contagious for up to 20 days, even without symptoms. Diagnostic methods include RT‑PCR, transcription‑mediated amplification and RT‑LAMP tests applied to nasopharyngeal swabs. Multiple vaccines have received approval and are being administered worldwide, alongside public‑health measures such as physical distancing, mask‑wearing, ventilation, hand hygiene and quarantine.

The disease continues to be monitored for long‑term health impacts and the effectiveness of preventive strategies.