It is only through the grace of a merciful God and the tireless efforts of dying doctor Henry Dawson and his small band of believers, not the Allied leadership, that the world of WWII never saw the above headline.
With the increase of the world's population since 1918, combined with the hunger and cold weakened state of so many of them, a return of the Spanish Flu would have killed far more than even WWII's enormous total of direct and indirect deaths.
Far worse, morally these deaths would not be due to an accident of nature as in WWI, but rather to a willful decision of the Allied leadership : a holocaust of deaths caused by willful medical negligence.