“The ordinance is immediately operative and will go into effect at midnight,″ announced Veneto regional Gov. Luca Zaia, whose area includes Venice. Carnival, which draws tens of thousands of visitors to the lagoon city, would have run through Tuesday. Museums, schools, universities and other public venues will be shut as well in Venice and the rest of Veneto. The shutdown is expected to last at least through March 1.

Authorities said three people in Venice have tested positive, all of them in their late 80s and who are hospitalized in critical condition. Nearly all of Italy’s 133 cases are clustered in the north, including in the Veneto region.

The biggest jump in cases of confirmed COVID-19 was reported by authorities in Lombardy, a populous region which includes the country’s financial capital, Milan. That region had at least 89 cases, nearly all of them in small towns in the countryside.