The plunge for stocks on Thursday tumbled, triggering a circuit breaker near the start of trading and putting the Dow Jones Industrial Average on the verge of registering its worst daily drop since the infamous 1987 crash. The Dow DJIA, -0.87% was down 9.5% at last check, off 2,245 points at 21,309. A drop of that magnitude on a percentage basis would represent the worst daily decline since the 23% crash on Oct. 19, 1987. The decline comes as all three major benchmarks are in freefall amid growing concerns surrounding containing and mitigating a global outbreak of COVID-19, an infectious disease that was first identified in Wuhan,China and has spread to roughly 128,000 people world-wide, shutting down supply chains and global economies in its wake. A speech by President Donald Trump late Wednesday failed to appease stock-market investors after he banned travel to Europe. Earlier Thursday, the S&P 500 tumbled 7% triggering an initial circuit breaker that pauses marketwide trade for 15 minutes. Most recently, the S&P 500 [: SPX] was down 7.2% and the Nasdaq Composite Index COMP, -1.07% was trading 6.8% lower. A secondary circuit breaker would trigger if the S&P falls 13%, resulting in another 15-minute trading halt.