“I refuse to kind of be around anybody that isn’t taking the pandemic seriously,” said Mikayla Cruickshank, an administrative coordinator in Lincoln, Neb.

Shobha Gupta, who runs an accounting business and lives in St. Petersburg, Fla., said she had continued socializing to some degree. The risk of not doing that, she said, was depression, especially as the pandemic stretched on.

“It doesn’t seem to end,” Ms. Gupta said.

In the more than two years since the coronavirus was first detected in the United States, the country has sped past milestones that once seemed unthinkable: 1,000 dead, 100,000 dead, 500,000 dead. As the country reaches the latest marker, with 900,000 deaths linked to the virus — more than the population of San Francisco — the collective shock has lessened, even as the impact on victims’ families has grown.

“Everybody was so up in arms when we hit those first couple of milestones,” said Elle Stecher, a marketing manager in Lincoln, Neb., who recovered from a bout with Covid in January. But now, she said, “none of it is registering anymore.”

Reporting was contributed by Lauryn Higgins in Lincoln, Neb., Elizabeth Djinis in St. Petersburg, Fla., Robert Chiarito in Chicago, Dan Simmons in Milwaukee, and Chloe Reynolds in New York.