U.S. stocks Wednesday midday skidded to session lows, erasing powerful gains from the previous session after the World Health Organization declared the outbreak of COVID-19 a pandemic. The Dow Jones Industrial Average DJIA, -0.87% was off 1,200 points, or 2.8%, at 23,828, the S&P 500 index SPX, -1.11% was off 4.3% at 2,757, while the Nasdaq Composite Index COMP, -1.07% declined 4% at 8,009. Until now, the WHO had characterized the illness, which was first identified in Wuhan, China in December, as a series of epidemics. An outbreak is deemed to have become a pandemic when it has spread from human-to-human on several continents. The agency said the number of cases outside China has increased tenfold and the number of countries affected has tripled. "We expect to see the number of cases, the number of deaths and the number of affected countries climb even higher.