A new respiratory disease, noticed at the end of 2019, spread worldwide in early 2020, and the World Health Organization declared it a pandemic. Its cause was a coronavirus named SARS-CoV-2. The disease starkly showed how quickly modern transport networks can globalize an outbreak.

The response was also global and rarely matched: wide-ranging movement restrictions, heavy strain on health systems, economic downturn, and lasting changes from education to ways of working. What stood out scientifically was the speed: the virus's genetic sequence was shared within days, and a vaccine-development process that could previously take decades reached use within a year through new platforms such as mRNA. Death-toll estimates vary greatly by method and source; the exact total is uncertain.

The pandemic was not only a health crisis but a test of global interdependence: supply chains, information flow, inequality, and trust in institutions all became visible at once. This experience became a reference point in the debate over preparedness for future global risks.