Germany

CHICAGO — When the coronavirus began sweeping around the globe this spring, people from Seattle to Rome to London canceled weddings and vacations, cut off visits with grandparents and hunkered down in their homes for what they thought would be a brief but essential period of isolation.

But summer did not extinguish the virus. And with fall has come another dangerous, uncontrolled surge of infections that in parts of the world is the worst of the pandemic so far.