The signs from Asia, where the disease first appeared, aren’t encouraging. China, Hong Kong, Singapore and Taiwan have been mobilized since January. The strain is showing, with complacency emerging as the first wave of infections ebbs. Imported cases are on the rise, raising the risk of a second wave. If that happens, President Xi Jinping’s celebrated visit to Wuhan this month may start to look as premature as U.S. President George W. Bush’s infamous “mission accomplished” speech in 2003.

No one knows the precise secret to sustaining good behavior in a pandemic of this scale and potential duration. Complicated ethical issues arise around personal freedoms and privacy. But we know from studies of past outbreaks, including severe acute respiratory syndrome in 2002-03, that there are steps authorities can take, including communication and targeted financial support that allow everyone to act responsibly.

It’s hard to overstate the importance of individual conduct when vaccines are unavailable, the supply of antiviral drugs and ventilators is limited, and transmission of the virus can happen before symptoms set in. With carriers hard to spot, social distancing — staying home, in essence — is the single most effective means of holding back the spread, preventing hospitals from becoming overwhelmed and sliding into emergency triage.