In Italy, millions are locked down and more than 1,000 people have died from the coronavirus.

But in South Korea, which was hit by the disease at about the same time, only a few thousand are quarantined and 67 people died.

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The story of the two outbreaks illustrates a difference in approach.

Italy started out testing widely, then narrowed the focus so that now, authorities do not have to process hundreds of thousands of tests. But there's a trade-off: They can't see what's coming and are trying to curb the movements of the country's entire population of 60 million people to contain the disease.

In South Korea, authorities are testing hundreds of thousands of people for infections and tracking potential carriers like detectives, using mobile phone and satellite technology.

Both countries saw their first cases of the disease called COVID-19 in late January.

South Korea has since reported nearly 8,000 confirmed cases, after testing more than 222,000 people.

In contrast, Italy has more than 12,000 confirmed cases after carrying out more than 73,000 tests on an unspecified number of people.

Epidemiologists say it is not possible to compare the numbers directly. But some say the different outcomes point to an important insight: Aggressive and sustained testing is a powerful tool for fighting the virus.

Jeremy Konyndyk, a senior policy fellow at the Center for Global Development in Washington, said extensive testing can give countries a better picture of the extent of an outbreak. When testing in a country is limited, he said, the authorities have to take bolder actions to limit the movement of people.

"I'm uncomfortable with enforced lockdown-type movement restrictions," said Konyndyk. "China did that, but China is able to do that. China has a population that will comply with that."

Previous lessons

Italy and South Korea are more than 5,000 miles (8,000 km) apart, but there are several similarities when it comes to coronavirus.

Both countries' main outbreaks were initially clustered in smaller cities or towns, rather than in a major metropolis - which meant the disease quickly threatened local health services.

Both confirmed their first cases after doctors decided to ignore testing guidelines.

South Korea, which has a slightly smaller population than Italy at about 50 million people, has around 29,000 people in self-quarantine. It has imposed lockdowns on some facilities and at least one apartment complex hit hardest by outbreaks. But so far no entire regions have been cut off.

Seoul says it is building on lessons learned from an outbreak of Middle East respiratory syndrome (MERS) in 2015 and working to make as much information available as possible to the public.

South Korea is also enforcing a law that grants the government wide authority to access data: CCTV footage, GPS tracking data from phones and cars, credit card transactions, immigration entry information, and other personal details of people confirmed to have an infectious disease.

The authorities can then make some of this public, so anyone who may have been exposed can get themselves - or their friends and family members - tested.

In addition to helping work out who to test, South Korea's data-driven systems help hospitals manage their pipeline of cases.

People found positive are placed in self-quarantine and monitored remotely through an app or checked regularly in telephone calls until a hospital bed becomes available. When this occurs, an ambulance picks the person up and takes them to a hospital with air-sealed isolation rooms.

This approach comes at the cost of some privacy. South Korea's system is an intrusive mandatory measure that depends on people surrendering what, for many in Europe and the US, would be a fundamental right of privacy.

"Traditional responses such as locking down affected areas and isolating patients can be only modestly effective, and may cause problems in open societies, says South Korea's Deputy Minister for Health and Welfare Kim Gang-lip.

In South Korea's experience, he told reporters on Monday, lockdowns mean people participate less in tracing contacts they may have had. "Such an approach," he said, "is close-minded, coercive and inflexible."