Top 3 coronavirus questions answered by an epidemiologist An epidemiologist answers the biggest questions she's getting about coronavirus. USA TODAY, Wochit

LONDON – Soon, the United States will find out whether it's likely to be the next South Korea or Italy or even China when it comes to the acceleration of coronavirus cases and deaths.

A data analysis by USA TODAY finds that, two weeks after the U.S. first entered into community transmission on March 3, America’s trajectory is trending toward Italy’s, where circumstances are dire. U.S. officials are sounding the alarm, urging Americans to heed what federal, state and local officials are asking of them in order to curtail the spread and dampen the impact of the virus on the U.S. population.

Although it's too early to draw definitive conclusions about which countries will ultimately weather the COVID-19 storm best, public health data shows that nations that are so far faring well at suppressing the outbreak's spread have done so through this combination: easy access to testing, rigorous contact tracing, clear and consistent science-based messaging, and a commitment to studiously abide by quarantines while clamping down on socializing no matter how tempting it may be to stray.

Daily coronavirus updates: Get USA TODAY's Daily Briefing in your inbox

Coronavirus curve for every state: Many could be close behind New York

. SOURCE Johns Hopkins University as of 5 p.m. ET March 18

"When you're on an exponential curve every moment is dangerous," said Francis Collins, the director of the National Institutes of Health, in an interview. "This is a particularly critical moment for us to try to bring all the resources and determination of government and the American people to try to get off of it."

Copy text Copy this quote's text The quote has been copied Tweet Share Francis Collins, the director of the National Institutes of Health When you're on an exponential curve every moment is dangerous. This is a particularly critical moment for us to try to bring all the resources and determination of government and the American people to try to get off of it. Quote icon

Outside of China, territories, city-states and countries in Asia such as Taiwan, Singapore, Hong Kong and Japan appear to be making the most progress. But experts say that U.S. comparisons to the experiences of other countries are not clear-cut for a variety of reasons, including population size, different medical systems, America's geographic expanse, and hard-to-account-for cultural reasons.

Coronavirus: These countries are doing the best and worst jobs fighting it

U.S. officials are monitoring what is playing out in other countries, particularly Italy, where rates of transmission and deaths in its northern regions have been so catastrophic that the Italian College of Anesthesia, Analgesia, Resuscitation and Intensive Care recently drew up guidelines for doctors about how to manage the crisis if the outbreak intensifies. Among the considerations discussed: prioritizing treatment for those under the age of 80 who don't have any "co-morbidities" – underlying health conditions. With too many patients to care for, many needing intensive care beds and ventilators that are in short supply, medical staff would need effectively to decide who lives and who dies. It's a form of triage medicine that is usually reserved for wartime.

Trump invokes wartime authority of Defense Production Act to address coronavirus crisis President Donald Trump announced he is invoking the Defense Production Act to address the coronavirus crisis. Associated Press, USA TODAY

"We're following every single country's curve," said Dr. Deborah Birx, the White House coronavirus task force response coordinator, during a briefing Wednesday.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. But for older adults, especially those with pre-existing health conditions, it can cause much more severe illness, including pneumonia.

The Centers for Disease Control and Prevention's worst-case-scenario is that about 160 million to 210 million Americans will be infected by December. Under this forecast, 21 million people would need hospitalization and 200,000 to 1.7 million could die by the end of the year.

"The extent to which we can prevent direct and excess deaths depends on how quickly we can flatten the outbreak, mobilize health services, and for how long we can prevent a relapse," said Robert Muggah, founder and director of the Brazil-based security think tank Igarape Institute and a leading expert on risk, who studies pandemics.

Coronavirus crisis: Trump invokes wartime authority of Defense Production Act

Estimates vary, but most public health experts believe that the U.S. is between one and two weeks behind what has befallen Italy, where a near-total lockdown has been imposed on 60 million citizens, with only supermarkets and drug stores open to the public. As of Wednesday, there have been more than 31,500 cases and 2,500 deaths.

Italian authorities began enforcing their lockdown on March 12, some 18 days after the point where community transmission, defined as more than 100 cases, had taken hold, according to World Health Organization data analyzed by USA TODAY.

It's too early to say whether restrictions in Italy, and similar ones in Spain, are working.

Collins said that if the U.S. takes measures that many Americans might find overly drastic "we should certainly be able to blunt" the U.S. curve. "But let's be clear: There's going to be a very rough road ahead of us over the next weeks and months."

In the U.S., 115 people have died amid more than 7,300 confirmed cases as of Wednesday, according to Johns Hopkins University's data dashboard.

There has been no federally mandated lockdown in the U.S., and access to testing has been sporadic, although President Donald Trump has urged Americans to refrain from gathering in groups of more than 10 people. San Francisco on Monday became the first U.S. city to order its residents to stay home over the coronavirus outbreak.

In China, where COVID-19 originated, the outbreak followed a pattern similar to Italy's.

The country initially saw an exponential rise in infections.

Beijing ordered a complete lockdown in Wuhan and other cities in Hubei province on Jan. 23, about halfway into the first 25 days of reported community transmission.

Yet after authorities embarked on one of the largest mass mobilization efforts in history, closing all schools, forcing millions of people inside, quickly building more than a dozen vast, temporary hospitals and meticulously testing and tracing anyone who may have encountered the virus, Beijing has appeared to all but eradicate new cases.

Wednesday, China’s National Health Commission reported just one new case in Wuhan for a second consecutive day and the country has slowly started to re-open schools and workplaces in some areas. Its death toll stands at 3,200, with over 81,000 infections.

Show caption Hide caption Medical staff members arrive for a duty shift at Dongsan Hospital in Daegu, South Korea, Wednesday, March 18, 2020. For most people, the new coronavirus... Medical staff members arrive for a duty shift at Dongsan Hospital in Daegu, South Korea, Wednesday, March 18, 2020. For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. (Lee Moo-ryul/Newsis via AP) ORG XMIT: SEL801 Lee Moo-ryul, AP

No one knows whether a second wave of infections will occur amid the easing restrictions.

In South Korea, which has a robust screening program, with more than 200,000 people tested – about one in every 250 people – testing is fast (about 10 minutes) and free (the government pays) and the results are usually sent by text within 24 hours. It was the first country to roll out a drive-through testing center and has a well-functioning virus-contact-tracing system. It hit 100 cases on Feb. 20, but unlike China, Italy and other European countries it managed early on to "flatten the curve," or spread out the number of its coronavirus cases over a longer period so that its health system can have time to mitigate the outbreak's impact, according to the World Health Organization data.

As of Wednesday, South Korea had 8,413 coronavirus cases, including 84 deaths. With the exception of Japan, no other country has been able to so successfully "flatten" a large number of cases so quickly, according to USA TODAY's analysis.

It's not immediately clear why.

But Michael Merson, director of the SingHealth Duke-NUS Global Health Institute and the Wolfgang Joklik Professor of Global Health at Duke University, said that places in Asia such as South Korea, Taiwan, Hong Kong, Japan and Singapore, which has seen about 315 cases but no deaths as of Wednesday, enjoy public health factors that are difficult for countries like the U.S., with its fractured system, to replicate.

"There's strong government leadership, but also trust in the government," Merson said.

"Every time a case is identified there is a very strong action plan to identify contacts. It's also very good at promoting hand-washing and keeping people at a safe distance from one another," he said, adding that Singapore has allowed businesses and universities to stay open but with strict guidelines about the size of gatherings (25 or under).

"They take prudent steps at prevention, but they haven't entirely shut the country down."