Schools and universities were ordered closed for at least a week in the wealthy regions of Lombardy and Veneto, museums and cinemas were shut and the last two days of the Venice Carnival were cancelled.
Italy’s civil protection unit said the number of cases of the highly contagious virus totalled 152, all but three of them coming to light since Friday.
Prime Minister Giuseppe Conte admitted he had been caught off guard by the sharp rise in virus infections.
“I was surprised by this explosion of cases,” he told state broadcaster RAI, warning that the numbers would likely rise in the coming days.
“We will do everything we can to contain the contagion,” he said.
The latest death was an elderly woman from the town of Crema, some 45km east of Italy’s financial capital Milan.
Like at least one of the other people who have died, she had been suffering from serious underlying health issues, officials said.
The number of certified cases of the illness in Lombardy rose to 110 from 54 a day earlier, while in Veneto some 21 people were diagnosed with the virus, including two people in Venice, which was packed with tourists for carnival season.
Health officials reported isolated cases in the neighbouring regions of Piedmont and Emilia Romagna.
Veneto’s governor Luca Zaia said he had dealt with numerous natural disasters during his long career, including floods and earthquakes.
“But this is the absolutely worst problem that Veneto has faced,” he told reporters.
Almost a dozen towns in Lombardy and Veneto with a combined population of some 50,000 have effectively been placed under quarantine, with locals urged to stay home and special permission needed to enter or leave the designated areas.
In Milan, residents rushed to stock up on essentials, while some parents decided to take their children out of the city.
“Today is madness. It feels like we’re in Baghdad. We can’t restock shelves quick enough,” a shop assistant in Milan said.
Milan’s famous La Scala opera house cancelled performances, and bars and discos in Lombardy were told to close by 6pm local time.
Some major sporting events were postponed, including four Serie A soccer matches scheduled for Sunday.
Meanwhile, four passengers from the Diamond Princess cruise ship who were flown to England have tested positive for coronavirus, bringing the total number of confirmed cases in the UK to 13.
The four have been transferred to specialist infection centres.
They had been among a group of 30 British nationals and two Irish citizens placed in quarantine in the country’s northwest on Saturday.
England’s chief medical officer said the virus was passed on in the Diamond Princess cruise ship, which had been held for more than two weeks off the coast of Japan.
“Four further patients in England have tested positive for Covid-19, bringing the total number of cases in the UK to 13,” Professor Chris Whitty said on Sunday.
The Department of Health said a “full infectious disease risk assessment” was done before Saturday’s repatriation flight and that no one who boarded the plane had displayed any symptoms of the virus.
Any more passengers who test positive will immediately be taken into specialist care, the department said.
It is understood some British nationals who are part of the Diamond Princess crew opted to remain on the ship.
Almost one-fifth of the 3711 passengers originally on board the cruise liner have been infected.
Japan’s health ministry announced on Sunday that a Japanese man in his 80s from the cruise who was taken to hospital after testing positive for the virus has died.
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