COVID-19: Symptoms, transmission, testing and vaccine overview

COVID‑19 is caused by the SARS‑CoV‑2 virus and spread worldwide from January 2020, prompting a global pandemic. Most infected people develop mild to moderate illness, but about 14% experience severe disease and 5% become critically ill. Older adults are at higher risk, and a significant share of patients develop long‑COVID symptoms lasting months.

The virus spreads mainly through airborne particles when people are in close proximity, especially indoors, and can also be transmitted via contaminated surfaces. People remain contagious for up to 20 days, even without symptoms. Diagnostic testing relies on nucleic‑acid methods such as RT‑PCR, transcription‑mediated amplification and RT‑LAMP.

Vaccines have been approved and are being administered in many countries, forming the core of mass‑vaccination campaigns. Public‑health measures continue to include physical distancing, mask‑wearing, ventilation of indoor spaces, hand hygiene and quarantine of exposed individuals.