Carl Bergstrom, biology professor, was quoted in a New York Times article about the coronavirus and social distancing.

In New Zealand, Prime Minister Jacinda Ardern has been using the term “bubbles” to describe the groupings of people who continue close contact.

“Don’t pop the bubble” is a common refrain.

But sooner or later, most of us figure out that bubble maintenance is no simple matter. Some people still face concrete challenges: They have to go to work or share custody of children. Many report squishier quandaries. Should they let a friend’s friend into their bubble? How should bubble-mates set rules and expectations? Can they fight the urge to make exceptions?

The longer this goes on, the harder it will get, said Jonathan Smith, a lecturer in epidemiology at the Yale University School of Public Health.

Staying inside our bubbles is like clearing highly flammable brush, said Carl Bergstrom, a biologist at the University of Washington who studies how infectious diseases spread.

“In a neighborhood where everyone’s house has a big cleared area with no brush in between, that fire can’t spread from one house to another.” When someone ventures beyond their bubble, they are scattering kindling, fueling the blaze.