nprnews_____ = ||| lubuntu at wor2 670N|||Fauci Warns The Delta Variant Is The Greatest Threat To The U.S. Efforts Against COVID||| kickerpage = |||no kicker pagenpr for NPRNEWS||| summarynpr = |||More contagious than other variants, and maybe more likely to cause severe disease, Delta is spreading so fast it could cause yet another U.S. surge this summer or fall, according to new research.