JOHANNESBURG — A deadly cyclone that struck Mozambique and other countries in southern Africa has nearly obliterated the worst-affected areas, flooding vast stretches of land, destroying roads and dams, and cutting off victims from help.

The cyclone, called Idai, has affected more than 1.5 million people, with a death toll now in the dozens but feared to be far higher.

The storm destroyed “90 percent” of Beira, a city of about a half-million people that is Mozambique’s fourth largest and faces the Indian Ocean, the International Federation of Red Cross and Red Crescent Societies said on Monday.