Sooner or later, it’s virtually bound to happen.

Though novel 2019 coronavirus cases in the United States have so far ticked up in fits and starts, experts on deadly diseases say Americans should be prepared to see an overnight boom in cases that mirror the skyrocketing outbreaks in Italy and South Korea.

At last count from the Centers for Disease Control and Prevention (CDC), there were 60 confirmed novel 2019 coronavirus cases in the U.S. One of those cases—in northern California—marked the first case of unknown origin, as The Washington Post first reported Wednesday. Fourteen patients came through the American health system after traveling to China or having close contact with someone who had. The rest were either repatriated individuals who fled the vicinity of the virus’s origin in China on State Department-chartered planes or else were rescued from the disastrous Diamond Princess cruise ship outbreak.

Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases at the CDC, acknowledged Tuesday that community spread—when cases are detected in an area but the source of the infection is not known—was very likely to cause more infections in the United States. The case in California, which a CDC statement said was “picked up by astute clinicians,” appeared to prove her right, and set the stage for a serious test of American health infrastructure after years of atrophy.

In Italy, officials have not been able to trace the origin of infections, which skyrocketed from just four on Friday to more than 528 by Thursday, killing at least 14 people. While each country faces its own health and containment challenges, experts say, there is little reason to believe the United States won’t soon face a similar coronavirus surge, even as President Trump on Wednesday urged calm and put Vice President Mike Pence in charge of the disease’s containment.

“It’s possible to say suddenly we’ll have 20 or 30 cases from one particular place,” said Dr. Jeffrey Klausner, an adjunct professor of epidemiology at the University of California Los Angeles who previously worked for the CDC. “People should expect that, but people should not be overly concerned about that. If we were testing everyone for the common cold, we would find hundreds of thousands of cases.”

Because not everyone is going to seek a test for cold symptoms, “it’s certainly possible that there are cases we don’t know about in the community,” added Klausner. But for most people, symptoms are mild to moderate. Less than 20 percent of confirmed cases have been severe, and just two percent fatal, he said.

“It’s a cold virus, and colds are readily transmissible from person-to-person,” Klausner continued. “There can be a rapid increase in the number of people with a cold virus, particularly in winter environments where people are more likely to be in close contact.”

For that reason, he continued, “Quarantine on the cruise ship was perhaps the stupidest idea ever.”

Ultimately, hundreds of people were infected on the ship—which until this week’s developments in South Korea represented the single largest outbreak outside China—before they were able to disembark.

“It spreads very rapidly because of the ease with which you can pass on this virus through respiratory droplets and surface spread,” said Dr. Adrian Hyzler, the chief medical officer for Healix International, which provides medical information to organizations whose clients travel internationally.

“You can see from the situation in the church group in Daegu that spread is like wildfire, especially in these close-knit situations, where numbers grew exponentially from 30 to well over a thousand in less than a week,” he added, referencing the outbreak in South Korea related to the Shincheonji church, where many of the country’s 1,146 cases are believed to have originated.

“There is every possibility that this could happen in the U.S,” added Hyzler, pointing to the outbreaks in Iran and Italy and the ease of transatlantic travel.

But the difference between isolated cases and community transmission, as far as experts currently understand it, comes down to two factors: How contagious is the initial case, and how closely are they associating with other people in a situation like a church assembly or dormitory—or a cruise ship?

Earlier this month, experts suggested some patients of this virus are ultra-contagious “super-spreaders.” That is, they more easily transmit the infection to others in a manner similar to the way “Typhoid Mary” became notorious for transmitting the bacteria that causes typhoid to at least 50 other people before she died in 1938.

“It would spread very rapidly on a crowded subway or metro system,” Hyzler said.

But even if a case popped up in, for example, New York City—where officials held briefings about the issue this week—experts dispute just how effective a quarantine or lockdown might be. Quarantines can help, but “if community transmission had already occurred in a city like NYC, then a citywide shutdown would be almost impossible to organize, and it would be much less effective,” Hyzler said.

“The more effective solution would be to widely distribute information to the population to carefully self-monitor and self-isolate as soon as any symptoms developed,” he continued.

Dr. William Haseltine, the president of the global health think tank ACCESS Health International who recently chaired the U.S.-China Health Summit in Wuhan, China, where the outbreak originated, said it more plainly: “The wrong way to handle it is a quarantine.”

“We should never consider stopping air travel or locking down cities,” said Haseltine. “Do we do that for the flu? No. Why would we do it for this? We know what its nature is. If we were treating this like we’d treat the flu, there’d be no lockdowns. There’d be no flight restrictions.”

Professor Eyal Leshem, a global expert on infectious diseases and the director of the Institute for Travel and Tropical Medicine at Israel’s Sheba Medical Center, Tel HaShomer, agreed that Americans should expect sustained community transmission “in the near future.” He added that authorities would do best to implement social distancing—school shutdowns, telecommuting to work, cancellation of public gatherings, and closure of public transportation—over a quarantine or travel lockdown.

“When the risk of sustained transmission of a highly infective disease in a community is very high, quarantine becomes less effective because it is impossible to trace all patient contacts,” Leshem said.

There’s also the question of available and effective diagnostic tests, which have been widely distributed by the thousands in countries like Italy and South Korea, but have encountered serious roadblocks in the U.S., where only about 500 people have been tested.

In the United Kingdom, Hyzler said the National Health Service was testing on site in people’s homes in order to prevent the potential of transmission in a hospital setting and to keep the ambulance service operational. After all, suspected patients would need to be transported by ambulance, and those vehicles would need to be disinfected before they could be put back in commission.

Haseltine lauded that plan, but said it’s probably not possible in the United States, saying: “We should be structured to do that, but we aren’t.”

“This isn’t HIV,” he said, suggesting coronavirus might not be deadly enough to truly push U.S. health care capacity to the brink, deficient though it may be. “Are we unprepared for a very serious epidemic? The answer is ‘yes.’ We’re unprepared. People would flood our hospitals,” said Haseltine.

Klausner agreed, noting that in the aftermath of the recession in 2008, “There’s been a decimation of public health infrastructure and capacity at the local and state level.”

“It simply does not exist anymore the way it should,” he added. “But that doesn’t mean we don’t have surge capacity. We just don’t have a really strong, ongoing capacity to deal with things on a day-to-day basis.”

Haseltine argued that, ultimately, a long-term overhaul to the entire public health system was necessary, on everything from training and education to the supply of respirators. Still, the worst case scenario likely won’t be as bad as some fear, he said, calling the possibility of a boom in U.S. cases that pushed the American medical system to the brink “very unlikely.”

“It’s much more likely that an even more deadly strain of flu would arise and strain our capacities,” he said.

“We should be prepared for something worse,” Haseltine continued. “We could have already been prepared for this if we’d taken warnings seriously.”