Singapore did almost everything right.

After recording its first coronavirus case on Jan. 23, the prosperous city-state meticulously traced the close contacts of every infected patient, while keeping a sense of normalcy on its streets. Borders were shut to populations likely to carry the contagion, although businesses stayed open. Ample testing and treatment were free for residents.

But over the past few days, Singapore’s coronavirus caseload has more than doubled, with more than 8,000 cases confirmed as of Monday, the highest in Southeast Asia. Most of the new infections are within crowded dormitories where migrant laborers live, unnoticed by many of the country’s richer residents and, it turns out, the government itself.

The spread of the coronavirus in this tidy city-state suggests that it might be difficult for the United States, Europe and the rest of the world to return to the way they were anytime soon, even when viral curves appear to have flattened. Although countries can closely track contacts to try to keep an outbreak at bay as Singapore did, the coronavirus is sickening, killing and spreading with each passing day, leaving scientists and political leaders racing to catch up with its relentless pace and new dangers.

If anything, the trials of this intensely urban, hyper-international country hint at a global future in which travel is taboo, borders are shut, quarantines endure and industries like tourism and entertainment are battered. Weddings, funerals and graduation parties will have to wait. Vulnerable populations, such as migrants, cannot be ignored.