Seasonal Influenza Zoonotic Influenza Pandemic Influenza Frequently Asked Questions on Zoonotic Influenza. SEA-CD-325 © World Health Organization 2017 Some rights reserved. This work is available under the Creative Commons Attribution-NonCommercial-Sha- reAlike 3.0 IGO licence (CC BY-NC-SA 3.0 IGO; https://creativecommons.org/licenses/by-nc-sa/3.0/igo). Under the terms of this licence, you may copy, redistribute and adapt the work for non-commercial pur- poses, provided the work is appropriately cited, as indicated below. In any use of this work, there should be no suggestion that WHO endorses any specific organization, products or services. The use of the WHO logo is not permitted. If you adapt the work, then you must license your work under the same or equivalent Creative Commons licence. If you create a translation of this work, you should add the following disclaimer along with the suggested citation: “This translation was not created by the World Health Organization (WHO). WHO is not responsible for the content or accuracy of this translation. The original English edition shall be the binding and authentic edition”. Any mediation relating to disputes arising under the licence shall be conducted in accordance with the mediation rules of the World Intellectual Property Organization.. Suggested citation. Frequently Asked Questions on Zoonotic Influenza. India: World Health Organization; 2017. Licence: CC BY-NC-SA 3.0 IGO. Cataloguing-in-Publication (CIP) data. CIP data are available at http://apps.who.int/iris. Sales, rights and licensing. To purchase WHO publications, see http://apps.who.int/bookorders. To submit requests for commercial use and queries on rights and licensing, see http://www.who.int/about/licensing. Third-party materials. If you wish to reuse material from this work that is attributed to a third party, such as tables, figures or images, it is your responsibility to determine whether permission is needed for that reuse and to obtain permission from the copyright holder. The risk of claims resulting from infringement of any third-party-owned component in the work rests solely with the user. General disclaimers. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of WHO concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted and dashed lines on maps represent approximate border lines for which there may not yet be full agreement. The mention of specific companies or of certain manufacturers’ products does not imply that they are endorsed or recommended by WHO in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters. All reasonable precautions have been taken by WHO to verify the information contained in this publica- tion. However, the published material is being distributed without warranty of any kind, either expressed or implied. The responsibility for the interpretation and use of the material lies with the reader. In no event shall WHO be liable for damages arising from its use. What is influenza? Influenza, commonly called “the flu” is an illness caused by influenza viruses that infect the respiratory tract of many animals, birds and humans. Human influenza is highly contagious and is usually spread by the coughs and sneezes of an infected person. 1 Influenza There are three types of influenza virus types A, B What are the known and C that can cause influenza, also known as “the types of influenza virus? flu”, in humans. Type A causes influenza in humans as well as in animals. Type A influenza in animals such as poultry, pigs and horses areparticularly relevant to public health. Influenza viruses that have the potential to cause a pandemic are referred to as ”influenza viruses with pandemic potential”. Historical data illustrates the 2 danger of transmission of influenza between animals and humans that can potentially contribute to the emergence of a pandemic. Influenza NA HA Types of Influenza Viruses M2 PB1 PA HA PB2 NP A responsible for regular Seasonal Influenza NA M NS outbreaks (Human) A Zoonotic Influenza 1 2 3 4 5 6 7 8 B causes sporadic outbreaks Pandemic Influenza C common but seldom causes disease symptoms A/California/4/09-likeH1N1 Influenza Viruses How do influenza All influenza viruses are genetically labile, that viruses change is, likely to change, with mutations occurring from time to time? from time to time. The constant small changes in the antigenic composition of influenza Drift viruses are known as the antigenic drift. On the Shift other hand, influenza type A viruses, including subtypes from different species, can swap or Influenza 3 “re-assort” genetic materials and merge during virus the re-assortment or mutation process. This phenomenon is known as the antigenic shift. Influenza Influenza type A viruses are classified into subtypes, depending How are type A on the combinations of different virus surface proteins known as influenza viruses haemagglutinin (H) and neuraminidase (N). There are 18 different classified? hemagglutinin subtypes and 11 different neuraminidase subtypes. Most subtypes of influenza A viruses have been found in birds, with the exception of subtypes A(H17N10) and A(H18N11) which have only been found in bats. Depending on the original animal host, influenza type A viruses can be classified as avian influenza or swine 4 influenza, and include other types of zoonotic influenza viruses. Examples of zoonotic influenza include avian influenza, also known as “bird flu”, with virus subtypes A(H5N1) and A(H9N2), and swine influenza, also known as “swine flu”, with virus subtypes A(H1N1) and A(H3N2). Human and swine influenza are sometimes caused by type A influenza viruses that have the same number of hemagglutinin (HA) and neuraminidase (NA) glycoprotein. Influenza How do we know a The type A influenza virus subtypes H1, H2 and H3 cause patient is infected by infections in both humans and pigs and can be differentiated by human influenza or swine name. Swine influenza viruses that infect humans through direct contact with infected pigs are considered “variant” viruses. influenza virus when it For example, H3N2v is a swine virus that can infect people is caused by the same but is different from the H3N2 human seasonal influenza virus. influenza virus? The names “variant” and “seasonal” are used to differentiate 5 between the known zoonotic influenza viruses, and influenza viruses that cause seasonal respiratory disease in humans. Human infections caused by variant viruses are of concern given that seasonal influenza vaccines developed to fight human influenza viruses are generally not expected to protect people from influenza viruses that normally infect pigs. Seasonal Influenza Influenza occurs globally with an annual attack rate What is the estimated at 5%–10% in adults and 20%–30% in burden of children. Illnesses can result in hospitalization and death, mainly among high- risk groups (the very influenza? 5%–10% young, the elderly, and among the chronically ill). in adults Epidemics can result in high levels of worker/ school Annual attack rate absenteeism and loss of productivity. Worldwide, these annual epidemics are estimated to result in 6 approximately 3 to 5 million cases of severe illness, and some 250 000 to 500 000 deaths1. The most 20%–30% effective way to prevent the disease and/or stave in children off its severity is through vaccination. 1www.worldbank.org/content/dam/Worldbank/document/HDN/Health/WDR14_bp_ Pandemic_Risk_Jonas.pdf Influenza What are the Human influenza is known as seasonal influenza as it has a seasonal types of human pattern of outbreaks. It may be caused by influenza virus types A, B influenza? or C. Human influenza A and B viruses circulate worldwide and can affect anybody in any age group and these viruses can cause annual epidemics that peak during winter in temperate regions. In tropical regions, influenza may occur throughout the year, causing outbreaks more irregularly. Influenza type C infections generally cause a mild 7 respiratory illness and are not thought to cause epidemics. That is why only influenza A and B viruses are included in seasonal influenza vaccines. Seasonal influenza is characterized by a sudden onset of high fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and a running nose. Seasonal Influenza An influenza pandemic can occur when a What is an influenza novel influenza virus gains the ability for pandemic? efficient and sustained human-to-human transmission and then spreads globally. Pandemic influenzas are caused only by a new strain of type A influenza virus. Because the virus is new, humans do not have immunity to it and the illness is usually more severe. A pandemic will not be a “one” time 8 event and periods of illnesses may come in two or three “waves” anywhere from three to twelve months apart. With international air flights, a “modern” pandemic is expected to spread to all parts of the world in less than three months. Pandemic Influenza What is zoonotic Zoonotic influenza occurs when humans are infected with influenza? influenza viruses circulating in animals. Human infections are primarily acquired through direct contact with infected animals or contaminated environments. This type of infection does not result in the efficient transmission of these viruses between humans. 9 Bird flu Zoonotic Equine influenza Swine flu Influenza Historical data shows that all pandemic influenza Why there is so occurrences originated from animals. All subtypes of much talk about influenza type A virus have zoonotic potential. Pigs are zoonotic influenza? ideal candidates for re-assortment or mutation of influenza viruses.