Interim Guidance for the Use of Masks to Control Seasonal Influenza Virus Transmission

Background

Seasonal influenza viruses are believed to be transmitted from person-to-person primarily through virus-laden droplets that are generated when infected persons speak, cough or sneeze; these droplets can be deposited onto the mucosal surfaces of the upper respiratory tract of susceptible persons who are near the droplet source. Transmission also may occur through direct and indirect contact with infectious respiratory secretions, (e.g., by hands that subsequently deliver infectious material to the eyes, nose or mouth).

A combination of infection prevention control strategies is recommended to decrease transmission of influenza viruses in healthcare settings. These include source control (immediately putting a surgical mask on patients being evaluated for respiratory symptoms), promptly placing suspected influenza patients in private rooms, and having healthcare personnel wear personal protective equipment (PPE) when caring for patients with suspected influenza. Additional information about PPE and other prevention strategies for personnel caring for patients with seasonal influenza is available. A mask should be worn by infectious patients any time they leave the isolation room.

The following recommendations focus on the appropriate use of masks as part of a group of influenza control strategies in healthcare settings. Masks are not usually recommended in non-healthcare settings; however, this guidance provides other strategies for limiting the spread of influenza viruses in the community.

Healthcare Settings

Symptomatic or Infected Patients

During periods of increased acute respiratory infections in the community, coughing patients and anyone suspected of having influenza should wear a mask at all times until they are isolated in a private room. Masks should be worn by these patients until

1. it is determined that the cause of symptoms is not an infection that requires isolation precautions or
2. the patient has been appropriately isolated, either by placement in a private room or in some circumstances by placement in a room with other patients with the same infection (cohorting). The patient does not need to wear a mask while isolated, except when being transported outside the isolation room.

Infection Prevention and Control Practices

Standard precautions should be used during the care of all patients in healthcare settings. Droplet Precautions should also be used during the care of any patient with suspected or confirmed seasonal influenza. While a patient with seasonal influenza is in a healthcare facility, Droplet Precautions should be maintained until one of the following is met, whichever is longer:

1. 7 days past illness onset or
2. at least 24 hours after resolution of fever without use of anti-pyretic medication and with improvement in respiratory symptoms.

In some cases, facilities may choose to apply droplet precautions for longer periods based on clinical judgment, such as in the case of young children or severely immunocompromised patients, who may shed influenza virus for longer periods of time.

Non-Healthcare Settings

Symptomatic Persons

Adults can shed influenza virus 1 day before symptoms appear and up to approximately 5 to 7 days after onset of illness; thus, the selective use of masks (e.g., in proximity to a known symptomatic person) may not effectively limit transmission in the community. Young children, immunocompromised persons of any age, and critically ill patients with influenza can shed influenza viruses in the respiratory tract for prolonged periods. Moreover, because no single intervention can provide complete protection against influenza virus transmission, emphasis should be placed on multiple strategies including pharmaceutical (e.g., vaccines and antiviral medications) and non-pharmaceutical interventions. The latter group include: 1) community measures (e.g., social distancing and school closures); 2) environmental measures (e.g., routine surface cleaning); and 3) personal protective measures such as encouraging symptomatic persons to:

• cover their nose and mouth when coughing or sneezing,
• use tissues to contain respiratory secretions and, after use, to dispose of them in the nearest waste receptacle, and
• perform hand hygiene (e.g., handwashing with non-antimicrobial soap and water, and alcohol-based hand rub if soap and water are not available) after having contact with respiratory secretions and contaminated objects/materials.

Persons who are diagnosed with influenza by a physician or who have a febrile respiratory illness during a period of increased influenza activity in the community should remain at home until the fever is resolved for 24 hours (without fever-reducing medications) and the cough is resolving to avoid exposing other members of the public. If such symptomatic persons cannot stay home during the acute phase of their illness, consideration should be given to having them wear a mask in public places when they may have close contact with other persons. In addition, masks are recommended for use by symptomatic, post-partum women while caring for and nursing their infant.

Unvaccinated Asymptomatic Persons, Including Those at Higher Risk for Influenza Complications

No recommendation can be made at this time for mask use in the community by asymptomatic persons, including those at higher risk for complications, to prevent exposure to influenza viruses. If persons at higher risk for influenza complications are unvaccinated and decide to wear masks during periods of increased respiratory illness activity in the community, it is likely they will need to wear them any time they are in a public place and when they are around other household members.

Annual influenza vaccination is the primary method for preventing influenza in persons at high risk for complications from influenza virus infection. However, influenza vaccine effectiveness is variable, and some vaccinated persons can get sick with influenza. Administration of antiviral medications for early treatment of influenza is a useful adjunct in the control of influenza in these persons. Antiviral treatment is recommended as soon as possible for hospitalized influenza patients, people who are very sick with influenza but who do not need to be hospitalized, and people who are at high risk of serious complications based on their age or health if they develop influenza.