As BA.5 becomes dominant among new U.S. cases, reduced state reporting is blurring the real-time look at the virus.

As states report less frequently, changes in the trajectory of the virus are slower to reveal themselves. Nearly every state reported the number of new coronavirus cases, hospitalizations and deaths for five days a week or more in 2020 and 2021, but 23 states now release new data only once a week, according to Times tracking.

California, which once updated its cumulative case and death figures every weekday, now does so only twice weekly. In Florida, case and death data are released just once every two weeks. Just last week, many more public testing sites closed in Alaska, Colorado and Rhode Island; Iowa is shutting many sites by the end of next week.

Recent virus figures have hiccuped around holidays like Memorial Day and Juneteenth, during which many states often pause reporting and then restart tracking afterward, a trend that is sure to continue this week, after the Fourth of July holiday weekend.

“Following the daily test count is less instructive than it was,” Dr. Adalja said, citing the close link between cases and hospitalizations in the past. Today’s numbers should not be treated like checking a sports team’s daily standings or scores, he added.

“I think testing is taking a different role,” he said. “Even when testing was at a different point, it has always been an underestimate.”

To get a localized look at how the virus is faring, Dr. Adjala said that he has come to rely on hospitalizations as a percentage of its capacity. He also checks the C.D.C.’s community levels tracker, which includes new hospital admissions and how many beds are used. He urges a shifting focus to severe disease, rather than tracking the “booms and busts of cases.”

Hospitalizations have increased modestly throughout June, though they remain low. Just over 33,000 people are in American hospitals with the coronavirus on an average day, and fewer than 4,000 are in intensive care. Reports of new deaths remain below 400 a day, down from the country’s daily death toll peak of more than 3,300 deaths in January 2021.

Lisa Waananen, Christine Chung and Alain Delaquérière contributed reporting.