COVID-19 has killed more people in Italy than any other country.

The death toll is now higher than China's, and the number of infections continues to grow.

Hospitals are now so overloaded that Italian doctors have been forced to choose who they treat.

The military had to move coffins from the cemetery in Bergamo to neighbouring provinces because there was no room left to bury them.

Italy's Prime Minister Giuseppe Conte imposed a nationwide lockdown to prevent what he called "the collapse of the system".

But one small town in the country's north says it is doing surprisingly well.

Vo, in the region of Veneto, is right in the middle of what Italy is calling its coronavirus red zone.

But local officials say there hasn't been a new case of COVID-19 there since March 13.

The town had the first confirmed COVID-19-related death in Italy — a 78-year-old man on February 23.

It was one of 11 villages in the country's north which were shut down as the country's outbreak began.

The town swung into action — and its measures appear to be working.

What did Vo do?

Researchers from the University of Padua, along with Veneto regional officials and the Red Cross, decided to test all residents for COVID-19.

Vo was one of 11 towns and villages in northern Italy locked down as the coronavirus outbreak there grew. ( LaPresse via AP: Claudio Fulan )

Around 3,300 people were tested, even if they had no symptoms.

"We tested everybody," Andrea Crisanti, professor of microbiology at the University of Padua, told the ABC's The World Today.

"We found that an alarming portion of people were already positive for the virus."

Nearly 3 per cent — or 89 Vo residents — were infected with COVID-19.

Even more alarming for Professor Crisanti and his colleagues was that many of the patients had no symptoms.

Professor Crisanti said Italian health authorities did not seem concerned by Vo's infection rate.

So the town took charge.

Vo put all COVID-19 patients in lockdown

Every Vo resident who tested positive for the virus was put in quarantine in their homes.

"They were asked not to go out, and not to have contact with any other people," Professor Crisanti said.

The researchers decided against sending patients to hospital to prevent them spreading the disease there.

"In principle many people in the hospital were infected. Many doctors, many nurses, many patients. This could be a major source of infection," he said.

The hospital system in northern Italy is so overloaded that the town of Vo was reluctant to send its patients there. ( Reuters: Francesca Mangiatordi )

After two weeks of quarantine, the researchers carried out another round of mass testing in Vo.

The rate of COVID-19 infection had dropped from nearly 3 per cent to 0.41 per cent.

Luca Zaia, the governor of Veneto, has now declared the town of Vo the "healthiest place in Italy".

''This is proof that the testing system works,'' he told the Italian news agency ANSA.

Vo says testing and social isolation is key

Professor Crisanti acknowledges that mass testing would be harder to carry out in a large city.

Vo officials say mass testing and extreme quarantine measures appear to have saved their town. ( Reuters: Vasily Fedosenko )

But he believes that Italy could have been much more proactive in containing the outbreak.

"As soon as we made data available that the infection rate in Vo was 3 per cent, they should have rung the alarm bell," he says.

"If at that time we had locked down all the cities with cases and carried out extensive testing, we would not be in this situation."

Some countries have restricted their tests.

In the UK, you can only be tested for COVID-19 if you are over 65 or have been admitted to hospital.

To conserve the number of testing kits in Australia, you have to meet certain criteria to get the swab.

That means only people who have had direct contact with a confirmed case of COVID-19, the elderly or patients admitted to hospital with respiratory illness will be tested.

South Korea, meanwhile, has been testing up to 20,000 people a day.

The World Heath Organisation this week called on all countries to ramp up the amount of testing they're doing.

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"We have a simple message to all countries — test, test, test," WHO's Director General Tedros Adhanom Ghebreyesus said.

"All countries should be able to test all suspected cases. They cannot fight this pandemic blindfolded."