As the novel coronavirus spreads globally — more than 100 countries have reported cases — governments are ramping up testing.

South Korea and China have tested hundreds of thousands of cases. According to the Centers for Disease Control and Prevention, the US has tested fewer than 2,000.

The US has performed five coronavirus tests per million people, compared with South Korea's 3,692 tests per million people.

More than 113,000 coronavirus infections and nearly 4,000 deaths have been confirmed. About 70% of cases and deaths are in China.

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As of Sunday, 1,707 Americans had been tested for the novel coronavirus, according to the Centers for Disease Control and Prevention. South Korea, by contrast, has tested more than 189,000 people. The two countries announced their first coronavirus cases on the same day.

In the US, test-kit shortages have hampered health authorities' ability to get a clear sense of how many Americans are infected. Compared with many other countries affected by the coronavirus, in fact, the US has done the fewest COVID-19 tests per capita.

South Korea's testing total so far, when broken down into number of tests performed per million citizens, seems to be about 700 times as high than the US's.

How many people have been tested per capita in 8 countries

Skye Gould/Business Insider

Because China has not published national data about its coronavirus testing, its Guangdong province is used here for purposes of comparison.

Not every country reports their testing numbers using the same metric. The UK reports it as "people tested," the US reports number of "patients," and Japan reports it as "persons." South Korea reports their testing total as "cases," Israel, Guangdong, and the Netherlands as number of "tests," and Italy as number of "swabs."

"The infectious-disease community and the public-health community desire to do much more testing than is currently feasible," William Schaffner, an infectious-disease specialist at the Vanderbilt University School of Medicine in Tennessee, told Business Insider on February 26.

"Other countries are testing much more broadly than we are," he added. "We are trotting along while they're racing along."

It's likely that the US has done more tests than the CDC's reported figure suggests, since the agency isn't tallying tests performed at state and private labs in the past week. The US Food and Drug Administration's commissioner, Stephen Hahn, said on Friday that the US had actually conducted 5,861 coronavirus tests, CNN reported. That number did not include tests conducted at private and commercial labs, Hahn added.

People in the New York City subway on March 3. Tayfun Coskun/Anadolu Agency via Getty Images

But even that higher number of tests per capita would still put the US behind the other seven countries listed above, with 18 tests per million people.

Testing influences what we know about the coronavirus' death rate

Without adequate testing, it's challenging for US public-health officials to grasp the scope of the outbreak's spread and determine how dangerous it is. More widespread testing could alter the disease's known death rate, a basic calculation that divides the number of reported deaths by the number of confirmed cases.

The US has one of the highest death rates in the world — about 3.6% as of Monday — but that's probably because so few mild cases have been counted.

Because testing capacity has been limited in the US, the CDC initially held stringent standards for who qualified. Until last week, the agency tested only people who had recent exposure to a confirmed patient, had traveled to a country with an outbreak, or required hospitalization.

So the US still probably has not tested or provided diagnoses to some patients with mild cases. Twenty-two Americans have died out of about 600 cases.

A healthcare worker preparing to transport a patient at Life Care Center of Kirkland, Washington, on February 29. David Ryder/Getty Images

South Korea, which has the third-highest number of cases behind Italy and China, has a death rate of just 0.7% — 50 people have died out of 7,478 cases.

Many patients are still hospitalized, however, so their conditions could change with time.

A disease's death rate is also different from its mortality rate — the latter is the number of deaths out of the number of people in an at-risk population. The death rate is not a reflection of the likelihood that any given person will die of infection.

Aria Bendix contributed reporting.