COVID-19 is a contagious disease caused by the SARS‑CoV‑2 virus. The infection spread worldwide from January 2020, leading to a global pandemic. Typical symptoms include fever, fatigue, cough, breathing difficulty, loss of smell and taste; about one‑third of infected persons remain asymptomatic. Of those who develop symptoms, roughly 81 % experience mild to moderate illness, 14 % develop severe disease such as dyspnea or extensive lung involvement, and 5 % become critical with respiratory failure or organ dysfunction. Older individuals are at higher risk of severe outcomes, and some patients suffer long‑term effects known as “long COVID.”
Transmission occurs primarily through inhalation of infectious aerosol particles, especially indoors, and can also happen via contact with contaminated surfaces. People may remain contagious for up to 20 days. Diagnostic testing relies on nucleic‑acid detection methods such as RT‑PCR, transcription‑mediated amplification, and RT‑LAMP from nasopharyngeal swabs. Multiple vaccines have been authorized and deployed worldwide, accompanied by public‑health measures including physical distancing, quarantine, ventilation, mask use, hand hygiene and cough etiquette.
These combined strategies aim to reduce spread, protect vulnerable populations, and manage the ongoing health impact of COVID‑19 globally.