A dozen towns in northern Italy effectively went into lockdown on Saturday after deaths of two people infected with the coronavirus from China, and a growing cluster of cases with no direct links to the origin of the outbreak abroad.

The secondary contagions prompted authorities in some Lombardy and Veneto towns to close schools, businesses and restaurants, and to cancel sporting events and religious services. The mayor of Milan, Italy’s business capital and the regional capital of Lombardy, shuttered public offices.

A 78-year-old man infected with the coronavirus died in Veneto, and a postmortem test performed on a 77-year-old woman in Lombardy came back positive, although it wasn’t clear if illness from the virus caused her death.

Hundreds of residents and workers who had come into contact with people who tested positive were put into isolation pending results of their tests. Civil protection crews set up a tent camp outside a closed hospital in Veneto to screen medical staff.

Facebook Twitter Pinterest Codogno, in the Lombardy region of Italy: the city centre is said to be like a ‘ghost town’. Photograph: Andrea Fasani/EPA

In the town of Codogno, where the first patient identified in the northern cluster was in a critical condition, closed supermarkets, restaurants and shops made the main street practically a ghost town. The few people outside wore face masks, which were coveted items after selling out at pharmacies.

Late Saturday, civil protection officials said 79 people had contracted the virus, including the two who died, and one who recovered. Of the remaining 76 people infected, 54 were in Lombardy, 17 in Veneto, two in Emilia-Romagna, two – a Chinese couple from Wuhan – in Lazio, and one in Piedmont.

Lombardy government authorities said the region’s cases were traceable to a 38-year-old Italian who had not travelled to China, but it remained unclear how this man had been infected. Ten towns in Lombardy received orders to suspend nonessential activities and services.

Luca Zaia, the Veneto regional president, said on Saturday that the contagion showed that the virus is transmitted like any flu, and that trying to pinpoint a single source for the cases or to establish a link to China were no longer effective containment measures.

“You can get it from anyone,” he told reporters. “We can expect to have cases of patients who had no contact [with suspected carriers].” He added that while the virus isn’t particularly lethal, it can be deadly for the elderly or people with existing conditions.

However, the man who died in Veneto had not met the main risk factors for the virus when he was diagnosed with pneumonia two weeks ago. He had not travelled to China, nor come into contact with anyone who had. Therefore he was only tested for the virus after he did not respond to conventional pneumonia treatment, and by then it was too late, according to Francesca Russo, the head of healthcare for the Veneto region.

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Along with eight other infected people, the man who died formed a cluster in his hometown of Vo’ Euganeo, population 3,300. Russo expressed relief that to date, none of the hospital personnel who treated the man have tested positive for the virus.

Giulio Gallera, the Lombardy health and welfare ministry chief, also said that the region’s cases comprised a traceable cluster, but that officials were still stumped about where it had originated from. The first person to fall ill had met with a man who had returned from China on 21 January, but this man tested negative for the virus and has been ruled out as the source.

Other people had acquired their infections from the 38-year-old, either through contact with him or at the hospital in Codogno where he first received treatment on 18 February.

More than 250 tests were completed in Lombardy, though hundreds more were being processed, including among the sick man’s colleagues at a Unilever plant near Codogno where he worked, Gallera said. “Given how contagious it is, it’s possible the numbers will increase,” he said.

National and regional officials approved an ordinance that put 10 Lombardy towns in effective lockdown around Lodi, southeast of Milan, after the region reported a quadrupling of cases on Friday. But individual cities outside the area covered by the ordinance, such as Cremona, issued their own restrictions after confirming there were local cases.

In Milan itself, however, Milan Fashion Week was wrapping up, though chatter about the rising numbers accompanied the runway shows.

“It doesn’t seem to me in this moment for what regards our sector, our fashion week, that there are signs of danger,’’ Carlo Capasa, president of the Italian National Fashion Chamber, told The Associated Press. ‘“We are tranquil and prudent.”

However, the world’s largest eyewear trade fair, MIDO, announced it was putting off its Milan show until June because of the outbreak, and the postponement of three Serie A football matches has been confirmed.

Despite the alarm, authorities urged calm and tried to balance precautionary closures with the economic reality of regions highly dependent on tourism and commerce. Hotel reservations in Venice were down one-third during the first weekend of Carnival, though the floods in the lagoon city late last year are likely to have scared off visitors.

“This is not an Italian ‘Wuhan’,” insisted Ivana Jelenic, president of the federation of Italian tourism and travel agencies, Fiavet. “Avoiding all travel at this time would just be alarmist.”

In Rome, doctors at the Spallanzani infectious disease hospital treating the first three people in Italy found to be infected with the virus – the Chinese couple from Wuhan and an Italian who contracted the virus in China – reported encouraging news on an otherwise bleak day. The Italian patient who tested positive for the virus two weeks ago was cleared to leave the hospital, while one of the Chinese visitors tested negative for the first time.

Separately on Saturday, 19 Italians who had spent more than two weeks quarantined on a virus-stricken cruise liner in Japan landed at Rome’s military Pratica di Mare airport. They had been stranded on the Diamond Princess since 5 February. Following first health checks and a decontamination process, the passengers were transferred to the military campus of Cecchignola, where they will spend a 14-day isolation period.