COVID-19 is a contagious disease caused by the SARS‑CoV‑2 virus, first spreading worldwide in January 2020. Common symptoms include fever, fatigue, cough, breathing difficulty, loss of smell and taste, with about 81% of patients experiencing mild to moderate illness, 14% severe disease, and 5% critical conditions. Older individuals face higher risk of severe outcomes, and some patients develop long‑COVID complications lasting months or years.
The virus spreads primarily through respiratory droplets and aerosols, remaining contagious for up to 20 days after infection. Testing relies on nucleic‑acid methods such as real‑time RT‑PCR, transcription‑mediated amplification, and RT‑LAMP. Multiple vaccines have been approved and are being administered globally, while preventive measures include physical distancing, mask use, ventilation, hand hygiene, and quarantine when needed. Treatment remains largely symptomatic.