Local health care facilities have issued a warning against influenza as Hampton Roads enters its third week of seeing widespread influenza-like illness.

Hospitals and health care systems “strongly recommend” that all patients and visitors wear a mask inside hospitals, medical facilities and physician practices to protect the community from the spread of flu.

The recommendation affects Sentara Obici Hospital, Sentara BelleHarbour and Bon Secours Health Center at Harbour View. All regional facilities in the Sentara, Bon Secours, Riverside and Children’s Hospital of the King’s Daughters systems are affected, as well as Chesapeake Regional Healthcare and the Naval Medical Center in Portsmouth.

Masks and hand sanitizer are available at facility entrances for public use. Even those who have already had a flu vaccine are encouraged to follow the recommendation.

“Vaccine is the best prevention available, but they are not 100 percent effective,” states a press release issued jointly by the health care systems. “Masking provides an added layer of protection from the potentially deadly disease.”

Those displaying symptoms of influenza-like illness are asked not to visit patients at area hospitals. Symptoms include fever, cough, sore throat, runny or stuffy nose, muscle aches, chills and, sometimes, vomiting and diarrhea.

Additional measures to take include washing hands frequently, staying home when sick, getting vaccinated and coughing into sleeves or tissues.