AdvertisementFauci Warns Dangerous Delta Variant Is The Greatest Threat To U.S. COVID EffortsUpdated June 22, 2021Rob SteinfacebookEmailDr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, warned on Tuesday of the danger from the Delta variant of the coronavirus. Among those not yet vaccinated, Delta may trigger serious illness in more people than other variants do. (AP)This article was originally published on June 22, 2021.