No one knows how serious the outbreak of swine flu that began in Mexico is going to be.

But events in Mexico City on Sunday are a pointed reminder that health alerts connected to infectious diseases can have a profound effect on the practice of the Catholic faith.

That’s because Catholic worship is a community affair, with a physical dimension that is fundamental to the celebration of Mass and other liturgical ceremonies.

All Masses in the Mexican capital were canceled Sunday, preventing Catholics there from participating directly in the celebration that is “the source and summit” of the life of the Church.

On Saturday, Zenit news service reported, Mexico’s Ministry of Health announced school closings in three Mexican states until May 6 and ordered museums, libraries, movie theaters, restaurants and places of worship in Mexico City to be closed until further notice.

Cardinal Norberto Rivera of Mexico City followed up with a statement later in the day, asking his priests to suspend all Masses without exception Sunday. Zenit noted the move is unprecedented in the overwhelmingly Catholic megalopolis, which has a metropolitan population exceeding 22 million.

Catholic News Service reported Cardinal Rivera conducted a private Mass behind closed doors Sunday Mexico City’s Metropolitan Cathedral.

“Later in the day, an image of Christ on the cross — known as the ‘Lord of Health’ — was removed from its spot in the cathedral for the first time since 1850 and carried in a procession around central Mexico City,” CNS reported. “The ‘Cristo,’ as the image is known, has been credited with past miracles, including intervention in an 1850 cholera outbreak.”

Cardinal Rivera also published a prayer directed to Our Lady of Guadalupe asking for her intercession to “quickly overcome this epidemic that has come to affect our nation.”

“Cover us with your cloak,” the prayer requests, “free us from this illness.”