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RR619 Evaluating the protection afforded by surgical masks against influenza bioaerosols

Background

The UK is preparing for a potential influenza pandemic. The main route of transmission of influenza is believed to be via direct contact with large droplets. The relative importance of aerosols in transmission is considered to be minor, but it cannot be ruled-out. The current UK Pandemic Influenza Infection Control Guidance recommends that workers who are in closecontact with patients should wear surgical masks to reduce exposure to large droplets. However, surgical masks are not intended to provide protection against infectious aerosols. The guidance recommends that procedures that are likely to generate aerosols should be minimised, or where unavoidable, workers should wear appropriate respiratory protection. There is a common misperception amongst workers and employers that surgical masks will protect against aerosols. This study aims to evaluate the relative levels of protection provided by both surgical masks and respirators against aerosols.

Main Findings

This study focussed on the effectiveness of surgical masks against a range of airborne particles. Using separate tests to measure levels of inert particles and live aerosolised influenza virus, our findings show that surgical masks provide around a 6-fold reduction in exposure. Live viruses could be detected in the air behind all surgical masks tested. By contrast, properly fitted respirators could provide at least a 100-fold reduction.

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