1. Background controversy about face masks There is ongoing debate and lack of consensus around the use of respiratory protection for HCWs for respiratory diseases, including influenza, which is reflected in incon-sistencies between policies and guidelines across health-care organizations and countries (Chughtai et al., 2013). In the healthcare setting facemasks (medical/surgical masks) are generally used to protect wearers from splashes and sprays of blood or body fluids and to prevent spread of