Which pandemic triggered the fastest bear market in U.S. stock-market history in early 2020?

The COVID-19 pandemic triggered the fastest bear market in U.S. stock-market history in early 2020.

As the novel coronavirus spread internationally, governments introduced travel restrictions, business closures, and other measures that sharply reduced economic activity. The S&P 500 entered a bear market on March 12, 2020, after falling at least 20% from its February record in only 16 trading days. The decline included several days when market-wide circuit breakers halted trading.

The Federal Reserve cut interest rates, bought financial assets, and introduced emergency lending programs, while governments provided large fiscal support. Markets then rebounded unusually quickly, although the economic damage was severe and uneven. The crash is often linked only to the virus, but the speed and depth of the decline also reflected uncertainty, forced selling, an oil-price shock, and concerns about credit markets.