Johns Hopkins hospitals and doctor offices will require everyone to return to wearing masks because COVID-19 and flu cases are high and vaccinations levels are low, officials wrote in a letter to patients Thursday.

The system follows others, including LifeBridge Health and the University of Maryland Medical System, directing patients, staff and visitors to mask up in patient areas.

“We anticipate this requirement to be in effect on a short-term basis while influenza-like illness rates are high,” Hopkins officials wrote. “We will continue to monitor the situation and adjust the requirement as needed.”

The masking policy reflects guidance from the Maryland Department of Health in late December. In a letter to health care providers, it said the combined virus-associated hospitalization rate exceeded 10 hospitalizations per 100,000 residents. It pointed specifically to COVID-19 and influenza cases.

In the week ending Dec. 16, the state’s rate was 11.4.

The department recommended “broad facility-wide” infection control measures in all patient care areas, including in outpatient and long-term care facilities, according to the guidance from Dr. Nilesh Kalyanaraman, the state’s deputy secretary for public health services.

The recommendations included universal masking and vaccinating eligible patients and health care workers against COVID-19, flu and RSV. It also recommended treating with antiviral medications early, testing and isolating infected individuals quickly, using protective equipment and optimizing ventilation.

The precautions could continue until two weeks after the virus-associated hospitalization rate drops below 10 hospitalizations per 100,000 residents for two consecutive weeks.

Hospitals had largely stopped testing every patient for COVID-19 as cases waned and more people had been vaccinated and infected and built immunity. With the public’s appetite for masking also dropping, many health systems no longer required that people cover their face.

Hospitalizations have become a key tracking method for infections since widespread testing dropped, though the U.S. Centers for Disease Control and Prevention also tests wastewater for COVID-19.

Experts say good-quality N95 or KN95 masks continue to be among the most effective means of preventing spread of infections. They had continued to advise people to wear them even when not required, especially when cases were high and people were going to be around at-risk family or friends.

“LifeBridge Health has been closely monitoring the steady increase of respiratory viruses, including COVID, RSV and the flu. In an effort to protect our team members, patients and communities, LifeBridge Health will be requiring masks in patient care areas, effective January. 8,” the system said in a statement.

The University of Maryland Medical System also returned to masking Jan. 8.

“Similar to what other health care institutions across the state are experiencing, hospitals across the University of Maryland Medical System are seeing an increase in patients presenting with respiratory illnesses. In response to increased hospitalizations for respiratory virus infections such as influenza, COVID-19 and respiratory syncytial virus, and following guidance from MDH, UMMS has made changes to both team member and visitor masking to reduce the spread of these viruses,” the University of Maryland Medical System said in a statement.