The places that escaped the Spanish flu
“These communities basically shut themselves down,” explains Howard Markel, an epidemiological historian at the University of Michigan who was one of the authors of the study. “No one came in and no one came out. Schools were closed and there were no public gatherings. We came up with the term ‘protective sequestration’, where a defined and healthy group of people are shielded from the risk of infection from outsiders.”

The people of Gunnison managed this by erecting guarded barricades on the main highways in and out of the surrounding county. Railway passengers were forced to submit to two days of quarantine upon arrival.

The sanatorium and school for the blind benefited from being relatively closed communities already, with walls to confine those who lived there also helping to protect those inside from the disease running rampant through the communities on the outside.

https://www.bbc.com/future/article/20181023-the-places-that-escaped-the-spanish-flu