an assessment of the evidence - Council of Canadian Academies

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Influenza Transmission and the Role of PPRE: An Assessment of the Evidence 9CHAPTER 1 - INTRODUCTIONHuman influenza is a respiratory disease caused by infection with influenza virus. 3Seasonal influenza occurs annually throughout the world. Influenza and itscomplications send about 20,000 Canadians, on average, to hospital every year,and approximately 4,000 die (PHAC, 2006). The average person will be exposedto the influenza virus many times over the course of his or her life and will thus buildup a degree of immunity toward similar strains of the virus. This increasedprotection can be attained either through natural exposure or regular influenzavaccinations. This acquired immunity, however, will not help in the event of a novelor “pandemic” influenza strain.Pandemic influenza occurs when a new strain of human influenza emergesfor which humans have little or no pre-existing natural or acquired immunityand that can spread efficiently from person to person and become geographicallywidespread. There were three pandemics in the 20 th century: Spanish influenza in1918-1919, causing an estimated 40 million or more deaths worldwide (Johnson,2002); Asian influenza in 1957-1958 (about 1.5 million deaths worldwide); andHong Kong influenza in 1968-1969 (about one million deaths worldwide).It is impossible to predict where and when the next pandemic might occur orhow virulent the virus will be. In light of the likelihood of another pandemic,governments and international bodies have developed various plans to helpminimize the health, social and economic consequences of such an event.The nature of pandemic influenza means that planning and response efforts needto be coordinated on local, national and international levels. Many countries havealready developed recommendations or policies for public health measures includingthe use of personal protective equipment, by both healthcare workers and thegeneral public, during a pandemic. 43 In this report, “influenza” refers exclusively to the human form of influenza unless otherwise noted.4 Annex B includes references and links to documents containing official recommendations andpolicies from various national and international bodies on matters relevant to the transmission ofinfluenza and personal protective equipment.
10 Influenza Transmission and the Role of PPRE: An Assessment of the EvidenceTERMS OF REFERENCEThe Public Health Agency of Canada (PHAC) has been working with federaldepartments and provincial and territorial governments to develop effectivepandemic preparedness strategies for both the general public and the healthcarecommunities. In particular, PHAC has developed the Canadian PandemicInfluenza Plan for the Health Sector which maps out how Canada is preparing for,and plans to respond to, pandemic influenza. There are, however, many challengesin planning due to gaps in scientific knowledge and understanding.In February 2007, PHAC charged the following questions to the Council ofCanadian Academies:a) How 5 and where 6 are seasonal influenza and pandemic influenza transmittedbased on existing reviews, or where needed, original literature 7 generated fromseasonal influenza outbreaks and from previous pandemics? andb) Based on the conclusions of this review, what is your assessment of thecontribution that N95 respirators or surgical masks will make to the preventionof transmission 8 of seasonal and pandemic influenza?PHAC requested an independent assessment of the current science and officialpositions on these issues as input to the working group on Annex F of the CanadianPandemic Influenza Plan. This group is responsible for gathering and consideringevidence to update this Annex which deals with “Infection Control andOccupational Health Guidelines During Pandemic Influenza in Traditional andNon-Traditional Health Care Settings.”5 e.g., aerosol (airborne), droplet, contact spread.6 e.g., homes, health care facilities, schools, other workforce, and community at large.7 As required, PHAC will provide copies of known key reviews which may not yet be published buthave been submitted and accepted for publication, i.e., those by Canadian experts and other internationalexperts and organizations such as the US Centers for Disease Control or UK Health ProtectionAgency or World Health Organization (WHO). These would serve to supplement the “reviewof reviews” which would be obtained through a comprehensive search of the existing literature (bothhealth and non-health).8 The contribution is to be assessed in the context of the infection control hierarchy; the componentsof which include, engineering controls, administration controls and personal protective equipment.
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