Hospitals in at least four US states have reinstated mask mandates.
It comes amid a rise in cases of Covid, seasonal flu and other respiratory illness.
Healthcare facilities in New York, California, Illinois and Massachusetts have made masks mandatory among patients and providers.
New York City Health Commissioner Dr Ashwin Vasan told WABC TV on Wednesday that mask mandates had resumed at all 11 of the city's public hospitals, 30 health centres and five long-term care facilities.
Medical workers put new PPE on for each visit to a Covid-19 patients room in the Covid-19 ward at the US Department of Veterans Affairs
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Dr Vasan said: "What we don't want is staffing shortages, right? When we saw the omicron wave in 2022, the biggest issues were not only people getting sick, but that we had a lot of frontline health workers, they were out with covid."
The most recent weekly data from the Centers for Disease Control and Prevention showed there were over 29,000 hospitalisations from Covid across the US from December 17-23.
This was up more than 16 per cent from the previous week. The CDC also reported over 14,700 flu hospitalisations in that same period.
The mask mandate has caused controversy with some believing that masks did little to suppress the spread of the illness.
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The CDC has reported over 14,700 flu hospitalizations in that same period.
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Rush University medical system in Chicago said on Tuesday that it was requiring "patients, visitors and staff to wear hospital-approved masks in some areas of the campus. They include clinical waiting areas and patient registration".
In Massachusetts, Berkshire Health Systems began mandatory masking on Wednesday, according to a statement.
In California, Los Angeles County on Saturday reinstated masking at all licensed health care facilities, according to a county statement provided to the City News Service.
The county's health department did not immediately respond to a request to comment from Reuters.
A conservative-dominated Supreme Court struck down President Joe Biden's federal vaccine-or-test mandate for companies.
A judge appointed by Trump struck down his public transportation mask mandate.
There was also deep resentment among those who did wear masks and felt their health was put in jeopardy by those who did not.
More than 1.1 million Americans have died from Covid, CDC figures show, a greater rate than most other wealthy countries.
