The second fact is that this disease is deadlier than the flu, to which the honestly ill-informed and the wantonly irresponsible insist on comparing it. Early guesstimates, made before data were widely available, suggested that the fatality rate for the coronavirus might wind up being about 1 percent. If that guess proves true, the coronavirus is 10 times as deadly as the flu.

But there is reason to fear that the fatality rate could be much higher. According to the World Health Organization, the current case fatality rate—a common measure of what portion of confirmed patients die from a particular disease—stands at 3.4 percent. This figure could be an overstatement, because mild cases of the disease are less likely to be diagnosed. Or it could be an understatement, because many patients have already been diagnosed with the virus but have not yet recovered (and may still die).

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When the coronavirus first spread to South Korea, many observers pointed to the comparatively low death rates in the country to justify undue optimism. In countries with highly developed medical systems, they claimed, a smaller portion of patients would die. But while more than half of all diagnosed patients in China have now been cured, most South Korean patients are still in the throes of the disease. Of the 7,478 confirmed cases, only 118 have recovered; the low death rate may yet rise.

Meanwhile, the news from Italy, another country with a highly developed medical system, has so far been shockingly bad. In the affluent region of Lombardy, for example, there have been 7,375 confirmed cases of the virus as of Sunday. Of these patients, 622 had recovered, 366 had died, and the majority were still sick. Even under the highly implausible assumption that all of the still-sick make a full recovery, this would suggest a case fatality rate of 5 percent—significantly higher, not lower, than in China.

The third fact is that so far only one measure has been effective against the coronavirus: extreme social distancing.

Before China canceled all public gatherings, asked most citizens to self-quarantine, and sealed off the most heavily affected region, the virus was spreading in exponential fashion. Once the government imposed social distancing, the number of new cases leveled off; now, at least according to official statistics, every day brings more news of existing patients who are healed than of patients who are newly infected.

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A few other countries have taken energetic steps to increase social distancing before the epidemic reached devastating proportions. In Singapore, for example, the government quickly canceled public events and installed medical stations to measure the body temperature of passersby while private companies handed out free hand sanitizer. As a result, the number of cases has grown much more slowly than in nearby countries.