Alameda County, Calif., home to Oakland, drops its indoor mask mandate after three weeks.

Less than a month after instituting a mask mandate for most indoor settings, health officials for Alameda County, the San Francisco Bay Area’s second-most populous county, lifted the order, citing improving conditions in a news release.

Mask requirements were reinstated earlier this month for restaurants, bars and offices and other places, in response to increased hospitalizations and new coronavirus cases across the county, which had exceeded last summer’s Delta variant wave.

The order was lifted Saturday after Alameda County, home to Oakland and 1.6 million people in the eastern Bay Area, moved from high risk to moderate risk for community transmission on Thursday, as defined by the Centers for Disease Control and Prevention guidance.

Daily case rates are falling, and, while the number of residents hospitalized with the virus remains high, daily new admissions have stabilized, county health officials said in a statement. Wastewater data mirrored these trends, they said. People who contract the coronavirus shed it in their stool, and the virus level in local wastewater is a reliable, independent signal of how much coronavirus is circulating in a given community.

As of Sunday, an average of 955 virus cases per day were reported in Alameda County, about the same as the average two weeks ago, and the number of patients hospitalized with the virus has risen about 5 percent over the last two weeks, according to a New York Times database.

“While we expect continued impacts from Covid-19 in the coming weeks, and masks remain strongly recommended, it is appropriate to step down from the health officer masking order at this time,” Dr. Nicholas Moss, the county health officer, said in a statement.

Officials still strongly recommend masks indoors for those who are older or have underlying health conditions, they said in the news release. They remain required in health care settings, long-term care facilities, jails, prisons and homeless shelters. The virus, they said, “continues to circulate, disrupt people’s lives and disproportionately impact communities of color, older adults, and those with underlying health conditions.”

More than 100,000 new coronavirus cases are being reported each day in the United States, according to a New York Times database, a figure that captures only a portion of the true number. Many infections go uncounted in official reports, and recent figures are further depressed by reporting delays caused by the Juneteenth holiday. Some scientists estimate that the current wave of cases is the second largest of the pandemic.

As of Sunday, hospitalizations in the United States are up six percent in the past two weeks, to an average of more than 31,000 each day, according to federal health data. New deaths have stayed below 400 per day on average, data from state and local health agencies show.

Alameda was the first county in California, and the largest jurisdiction in the United States, to issue a universal indoor mask order since the end of the winter Omicron surge. There has not been a widespread return to mask mandates in California, although some schools and universities reinstated them in the spring.

In Los Angeles County, the nation’s most populous county with about 10 million people, public health officials said last week that mask rules could return if C.D.C. data showed that it recorded high coronavirus community levels for two straight weeks. But the county remains at a “medium” level, making a mandate unlikely through mid-July.

Philadelphia also briefly reinstated indoor masking this spring, only to drop it days later. In April, a federal judge struck down a mask requirement on airplanes, trains, buses and other public transportation.

More recently, the requirement to test for the coronavirus before flying to the United States was dropped, and Broadway theaters, save for one, are retiring their mask requirements beginning Friday.