Thursday, August 20, 2009

Information on the effectiveness of facemasks

According to CDC (Centers for Disease Control and Prevention), limited data is available on the effectiveness of wearing facemasks in preventing transmission of H1N1 in various settings.

However, the use of a facemask is likely to be of most benefit if used as early as possible when exposed to an ill person and when the facemask is used consistently

Facemasks help stop droplets from being spread by the person wearing them. They also keep splashes or sprays from reaching the mouth and nose of the person wearing the facemask. They are not designed to protect against breathing in very small particle aerosols that may contain viruses. Facemasks should be used once and then thrown away in the trash.

CDC Interim Recommendations for Facemask and Respirator Use for Home, Community, and Occupational Settings for Non-Ill Persons to Prevent Infection with Novel H1N1 1 2

Setting Persons not at increased risk of severe illness from influenza
(Non-high risk persons)
Persons at increased risk of severe illness from influenza (High-Risk Persons) 3
Community
No novel H1N1 in community Facemask/respirator not recommended Facemask/respirator not recommended
Novel H1N1 in community: not crowded setting Facemask/respirator not recommended Facemask/respirator not recommended
Novel H1N1 in community: crowded setting Facemask/respirator not recommended Avoid setting.
If unavoidable, consider facemask or respirator 4 5
Home
Caregiver to person with influenza-like illness Facemask/respirator not recommended Avoid being caregiver. If unavoidable, use facemask or respirator 4 5
Other household members in home Facemask/respirator not recommended Facemask/respirator not recommended
Occupational (non-health care)
No novel H1N1 in community Facemask/respirator not recommended Facemask/respirator not recommended
Novel H1N1 in community Facemask/respirator not recommended but could be considered under certain circumstances 4 5 Facemask/respirator not recommended but could be considered under certain circumstances 4 5
Occupational (health care) 6
Caring 7 for persons with known, probable or suspected novel H1N1 or influenza-like illness Respirator Consider temporary reassignment. Respirator

1 The effectiveness of facemasks in preventing transmission of novel H1N1 (or seasonal influenza) in various settings is not known. Use of a facemask is likely to be of most benefit if used correctly and consistently when exposed to an ill person. (Ref. a) MacIntyre CR, et al. EID 2009;15:233-41. b) Cowling BJ, et al. Non-pharmaceutical interventions to prevent household transmission of influenza. The 8th Asia Pacific Congress of Medical Virology, Hong Kong, 26-28 February 2009.)

2 For the purpose of this document, respirator refers to N95 or any other NIOSH-certified filtering face piece respirator.

3 Persons at increased risk of severe illness from influenza (i.e. high-risk persons) include those groups at higher risk for severe illness from seasonal influenza, including: children younger than 5 years old; persons aged 65 years or older; children and adolescents (younger than 18 years) who are receiving long-term aspirin therapy and who might be at risk for experiencing Reye syndrome after influenza virus infection; pregnant women; adults and children who have pulmonary, including asthma, cardiovascular, hepatic, hematological, neurologic, neuromuscular, or metabolic disorders, such as diabetes; adults and children who have immunosuppression (including immunosuppression caused by medications or by HIV); and, residents of nursing homes and other chronic-care facilities.

4 The optimal use of respirators requires fit testing, training and medical clearance. Proper use is recommended to maximize effectiveness. The use of facemasks may be considered as an alternative to respirators, although they are not as effective as respirators in preventing inhalation of small particles, which is one potential route of influenza transmission. There is limited evidence available to suggest that use of a respirator without fit-testing may still provide better protection than a facemask against inhalation of small particles. Respirators are not recommended for children or persons who have facial hair (see FDA website).

5 Use of N95 respirators or facemasks generally is not recommended for workers in non-healthcare occupational settings for general work activities. For specific work activities that involve contact with people who have influenza-like illness (ILI) (fever plus at least either cough or sore throat and possibly other symptoms like runny nose, body aches, headaches, chills, fatigue, vomiting and diarrhea), such as escorting a person with ILI, interviewing a person with ILI, providing assistance to an individual with ILI, the following are recommended: a) workers should try to maintain a distance of 6 feet or more from the person with ILI; b) workers should keep their interactions with the ill person as brief as possible; c) the ill person should be asked to follow good cough etiquette and hand hygiene and to wear a facemask, if able, and one is available; d) workers at increased risk of severe illness from influenza infection (see footnote 3) should avoid people with ILI (possibly by temporary reassignment); and, e) where workers cannot avoid close contact with persons with ILI, some workers may choose to wear a facemask or N95 respirator on a voluntary basis (See footnote 1). When respirators are used on a voluntary basis in an occupational work setting, requirements for voluntary use of respirators in work sites can be found on the OSHA website.

6 See case definitions of confirmed, probable, and suspected novel influenza A (H1N1). Also see infection control in the health care setting. When respiratory protection is required in an occupational setting, respirators must be used in the context of a comprehensive respiratory protection program as required under OSHA’s Respiratory Protection standard (29 CFR 1910.134). This includes fit testing, medical evaluation and training of the worker.

7 “Caring” includes all activities that bring a worker into proximity to a patient with known, probable, or suspected novel H1N1 or ILI, including both providing direct medical care and support activities like delivering a meal tray or cleaning a patient’s room.

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