Since South Korea confirmed its first case of coronavirus on Jan. 20 the total number of infected in the country has ballooned exponentially, hitting 7,513 as of March 10. The government responded swiftly, testing over 120,000 people for the virus and directing over 30,000 people to self-quarantine. Evidently impressed with the response himself, Health Minister Park Neunghoo on Tuesday dared to hope that the virus had reached its peak.

“We are hoping that we have passed the peak, taking the numbers into consideration, and cautiously expecting we have passed the peak,” Park told CNN. It’s unclear which numbers Park was taking into consideration, but the rate of new cases in South Korea appeared to be in decline.

According to the local Centers for Disease Control and Prevention (KCDC), there were 131 new cases as of March 10, compared to 248 and 367 new cases the previous two days, respectively. However, the KCDC noted the decline in Daegu and Gyeongbuk region—where the majority of cases are—is because nearly all members of the Shincheonji church at the center of the outbreak now have been tested.

“However, since the confirmed cases continue to be reported from health facilities and community centers, the local governments are taking response measures to prevent further transmission at such facilities. In Seoul and Gyeonggi region as well, small-scale, sporadic outbreaks have been identified mainly at the places where high-risk groups visit often, such as health facilities and community centers,” the KCDC said March 9, providing a warning that an outbreak could still occur elsewhere in South Korea.

Sure enough, two days later, the KCDC confirmed 242 new cases, reversing the downward trend of new infections. The jump came as authorities tested hundreds of staff at a call center in Seoul, where they discovered 52 new cases. Meanwhile, Daegu reported 140 more infections, also reversing the city’s downward trend.

Twin Peaks

Declaring a peak doesn’t mean total infection numbers are coming down, but rather that new cases are tapering off. For instance, Tedros Adhanom Ghebreyesus, the general director of the World Health Organization, declared on Feb. 19 that China had reached peak Covid-19, as the rate of new infections had begun to decline. However, the total number of infected in China since then has continued to rise, from 74,280 that day to 80,904 on Tuesday, according to WHO data.

China’s infection rate has been confused by several changes to how officials document cases, too. On Feb. 12, officials in Hubei province—the center of the outbreak—decided to include clinical diagnoses among the total count of infected patients, sending the total number skyrocketing. But the next day the decision was reversed, and infection numbers tumbled.

As it stands, China has reported more recoveries from coronavirus than it has current infections. Over 60,000 patients have recovered while a little under 20,700 are known to still be infected, according to data compiled by John Hopkins University. But even if the infection rate has peaked in China, that’s not to say it can’t peak again.

“In China, the virus has already peaked once and the first wave is over. The questions is, will there be a second wave and, if so, how big?” says Gabriel Leung, Dean of Medicine at Hong Kong University.

Because humans have no immunity to Covid-19 the potential for a second major outbreak in China still exists and Beijing is aware of that risk. In recent weeks the government has moved to restrict or discourage arrivals from other countries currently experiencing their “first wave” of Covid-19, such as Japan, South Korea and the U.S., as Beijing fears sparking another outbreak at home.

Breaking America

When the outbreak began, epidemiologists were quick to estimate how far it would spread and predict a moment when the contagion would peak. Hiroshi Nishiura, an epidemiologist at Hokkaido University in Sapporo, Japan, predicted in February that the contagion would peak between late-March and late-May, with global infection rates hitting 2.3 million a day.

That same month, Harvard University epidemiologist Marc Lipsitch suggested the outbreak could infect up to 70% of the world’s population, while Leung gives a similar figure of around 60% total infection. However, that number requires context, Leung says.

“That number in of itself is meaningless unless you contextualize it with three things. One, over what period is this going to be realized? A week, a month, a year, a decade? Theoretically, unless you have a vaccine you remain at risk and, sooner or later, at some point you will be infected. But the speed and the time period is the critical qualifier,” Leung says.

If 70% of the population becomes infected, they wouldn’t all be infected at the same time, because the world is not experiencing the coronavirus in-synch. Outbreaks are only just beginning in countries like Italy, Iran and France while in some countries—such as the U.S.—serious epidemics haven’t appeared at all yet because they’re not doing significant testing, Leung says.

The other two factors to remember, Leung says, are severity and intervention. If the virus isn’t severe then contagion doesn’t matter. Last week the WHO gave a mortality rate of 3.4% for Covid-19—higher than the seasonal flu, so severity is an issue.

Meanwhile, intervention measures adopted in places like China, Italy and South Korea have reduced transmission significantly, throwing off models. But those drastic quarantine measures aren’t sustainable. China is tentatively sending people back to work already, which could unleash a second wave.

“Is a peak coming and are we going to be able to hold it at bay forever?” Leung asks. “Nobody knows yet.”

More must-read stories from Fortune:

—How coronavirus is affecting the global concert industry

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—Some of the most extreme ways companies are combating coronavirus

—How Europe is adapting to the coronavirus outbreak

—China’s box office was supposed to surpass North America’s this year.

—Growing coronavirus threat weighs on Apple

—Nearly half of American travellers are reconsidering their international trips due to coronavirus



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