The United States has the most confirmed Covid-19 cases in the world, with more than 15 times the number of cases reported in China and about six times as many cases as Italy and Spain, other epicenters of the global outbreak. Confirmed infections in the US make up around a third of the world’s coronavirus cases.

America started off testing people for the coronavirus at a slower rate than most other developed countries, but the number of people diagnosed with Covid-19 in the US has risen more quickly than the country’s peers abroad. We don’t yet know the full extent of the outbreak, but America remains a focal point of the coronavirus pandemic.

The US health system was less prepared for a pandemic than those of other wealthy nations. A high uninsured rate, high out-of-pocket health care costs, and low medical system capacity together make the country more vulnerable to a pathogen before the coronavirus ever came to our shores. America’s lax response in the early days of the outbreak only compounded those structural problems.

“Everyone working in this space would agree that no matter how you measure it, the US is far behind on this,” Jen Kates, director of global health and HIV policy at the Kaiser Family Foundation, told Vox in mid-March of the initial coronavirus response.

Here’s how the number of confirmed cases in the US compares to select other countries, based on days since each country reached 100 confirmed cases, according to data we analyzed from the Johns Hopkins University coronavirus dashboard.

Note that the chart uses a log scale, meaning that the Y-axis goes up in equal distances between 100, 1,000, and 10,000 to mimic the exponential rate at which a contagion like the coronavirus spreads.

Here’s that same chart on a traditional linear scale.

As of May 11, the Johns Hopkins research data shows more than 4.1 million confirmed cases worldwide, about 1.3 million of which were in the US. The actual number of cases is likely much higher. About 280,000 people have died across the world from Covid-19, including nearly 80,000 in the United States. There are signs that social distancing measures in the US are making an impact, but the country surpassed Iran, Italy, and China to have the highest number of confirmed cases in the world.

As the Wall Street Journal has reported, Chinese health officials have acknowledged they did not include 1,500 asymptomatic cases in their previous national tallies, but said that such cases would be counted starting on April 1. Based on reporting by the South China Morning Post, China may be undercounting asymptomatic cases to an even greater degree. But remember, most countries’ numbers are probably low because people who have no or mild symptoms often don’t get tested.

Case numbers in the US have also far outpaced places like South Korea, Hong Kong, and Singapore, where the governments mobilized more quickly and certain cultural norms (like mask-wearing) may have helped slow the spread. (Early signs of a second wave of cases have appeared in Singapore, however; this was a fear among public health experts who worried societies would be too quick to reopen.)

Japan’s case numbers have started rising more quickly in recent weeks, and the government has been criticized over not having enough tests to properly judge the number of cases.

As America implements dramatic measures to control the spread of Covid-19, with schools and businesses closing and general social distancing underway, the country is still struggling to understand the full scope of the outbreak because of the slow start of testing. It has undeniably hindered the US response.

“The testing failure is putting additional strain on our already challenged health system,” Cynthia Cox, director of the Peterson-Kaiser Health System Tracker, said in March. “The combination of all of these factors will make the US worse off than similar countries.”

Testing is not only important because it gets people diagnosed and appropriate treatment if they have an infection, it also establishes how widespread a virus actually is. Experts know the size of the problem, they know the rate at which people are being hospitalized or dying, and they can follow its movements.

But the United States faltered in rolling out coronavirus tests, initially putting America behind its economic peers in tracing the outbreak. A manufacturing problem with the test kits that were initially sent out in the field, and a delay in approving commercial tests, set the nation back in stopping or slowing down Covid-19.

Even as testing capacity has ramped up in the US, as of May 4 America is still lagging behind other places in the world hit hardest by the virus in the share of its population being tested. The US has still tested fewer people per million residents than Italy, a focal point of Europe’s outbreak, and Germany, which is considered a model of rapid and widespread testing.

There have been about 9 million tests conducted in the US for its population of 329 million, but the number of tests per capita conducted varies greatly by state.

The US has finally started to catch up to the rest of the developed world in responding to Covid-19. But as case numbers and deaths continue to increase, we’re still learning the full scope of the crisis.

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