CAIRO — It was a rare moment in the 1,400-year history of Islam, and another sobering milestone in the march of the coronavirus.

On Friday, the first day of Ramadan, silence shrouded the Kaaba, the black cube-shaped structure that Muslims face while praying, as the virus cast a long shadow over a sacred month of fasting, prayer and socializing that is central to the faith of the world’s 1.8 billion Muslims.

The sealed-off Kaaba, in the Saudi city of Mecca, and another revered site in nearby Medina were among tens of thousands of places in Muslim-majority countries where communal prayers have been banned and family gatherings curtailed, plunging worshipers into a Ramadan like no other.