ROME — As Italy’s coronavirus infections ticked above 400 cases and deaths hit the double digits, the leader of the governing Democratic Party posted a picture of himself clinking glasses for “an aperitivo in Milan,” urging people “not to change our habits.”

That was on Feb. 27. Not 10 days later, as the toll hit 5,883 infections and 233 dead, the party boss, Nicola Zingaretti, posted a new video, this time informing Italy that he, too, had the virus.

Italy now has more than 53,000 recorded infections and more than 4,800 dead, and the rate of increase keeps growing, with more than half the cases and fatalities coming in the past week. On Saturday, officials reported 793 additional deaths, by far the largest single-day increase so far. Italy has surpassed China as the country with the highest death toll, becoming the epicenter of a shifting pandemic.

The government has sent in the army to enforce the lockdown in Lombardy, the northern region at the center of the outbreak, where bodies have piled up in churches. On Friday night, the authorities tightened the nationwide lockdown, closing parks, banning outdoor activities including walking or jogging far from home.