that is more deaths than in the 1918 flu pandemic. it s approximately 1 in 490 americans, mothers, fathers, friends, brothers, all gone. that many people could fill almost ten nfl stadiums. nearly 2,000 americans are dying every day now. cnn s dr. sanjay gupta takes a look at how we reached this devastating toll. reporter: a little more than a century ago, an influenza pandemic ravaged america. there were four waves in the 1918/1919 pandemic. the two greatest occurred in the fall of 1918 and the winter of 1919. reporter: dr. howard marquel studied epidemics in american history. there were no vaccines for influenza. we didn t know it was caused by a virus. reporter: best projections, 675,000 people died. fast forward to today, a grim milestone.