ARMANT FEVERS HOSPITAL :ARMANT FEVERS HOSPITAL Epidemiology OF AVIAN FLUE DR . M. ESSA


3 Types of Influenza Virus :3 Types of Influenza Virus Type A Most serious of the 3 types of flu. Strains are identified by their spikes Type B Only one strain identified Type C Mild virus, not ever included in vaccine


Slide 4:The Virus


Type A Flu Virus Has two Kinds of Spikes :Type A Flu Virus Has two Kinds of Spikes Hemagluttinin (H) Spikes help the virus attach to human cells 500 per virus Neuraminidase (N) Spikes help the virus exit an infected cell 100 per virus http://microbiology.mtsinai.on.ca/bug/flu/flu-dis.shtml


Types of Influenza Virus :Types of Influenza Virus Three types: A, B, C Influenza Type A can infect: People, birds, pigs, horses, seals, whales and others Influenza Type B: Human virus Not classified according to Subtype Cause human epidemics but not pandemics Influenza Type C cause mild illness in humans Not classified according to subtype Do not cause epidemics or pandemics


Subtypes of Influenza A :Subtypes of Influenza A Subtypes defined by different antigens in humans, animals and birds H (haemaglutinin): HA – 15 variations N (neuraminidase): NA – 9 variations 15 subtypes of influenza virus infect birds Examples H1N1, H1N2, H3N2 (common human) H7N7 (avian 2003, The Netherlands) H5N2 (avian vaccine) H5N1 (current avian)


Avian Influenza A Viruses :Avian Influenza A Viruses Infect respiratory and gastrointestinal tracts of birds Genetic reassortment occurs frequently Can cause morbidity and mortality in domestic poultry Avian influenza A viruses are shed in the respiratory tract and in feces Can survive at low temperature and low humidity for days to weeks Can survive in water Can survive on surfaces Disinfection of the environment is needed


Low Vs. High Pathogenic Avian Influenza :Low Vs. High Pathogenic Avian Influenza Low Pathogenic Avian Influenza Viruses (LPAI): May not cause any illness in wild birds Associated with mild illness in domestic poultry Can evolve into highly pathogenic viruses Associated with poultry outbreaks worldwide Subtypes: H9 High Pathogenic Avian Influenza Viruses (HPAI): May not cause any illness in wild birds High mortality in domestic poultry High risk of disease in people Subtypes: H5, H7


Antigenic Drift :Antigenic Drift Point mutations in the hemagglutinin gene cause minor antigenic changes to HA Continuous process Immunity against one strain may be limited Antigenic drift produces new virus strains that may not be recognized by antibodies to earlier influenza strains This is one of the main reasons why people can get the flu more than one time (Seasonal epidemics). one or two of the three virus strains in the influenza vaccine are updated: 6-8 months process Targeted at high-risk (inactivated)


Antigenic Shift :Antigenic Shift new influenza virus that can infect humans and has (new HA subtype ± NA) through: Genetic reassortment (human and animal viruses) Direct animal (poultry) to human transmission if most people have little or no protection against the new virus: Spread easily from person to person Pandemic (worldwide spread) may occur


Slide 14:From Birds to Human Hong Kong 1997/2003, H5N1 HK, China 1999, H9N2 Netherlands2003, H7N7 Vietnam & Thailand2004, H5N1 Indonesia 2005, H5N1 Source: WHO/WPRO


Slide 15:Reassortment (in Animals and Humans) Reassortment in Swine Reassortment in humans Human Pandemic Strain


Public Health Risk :Public Health Risk Emergence of a new influenza virus Highly pathogenic Rapid spread from person-to-person


Environmental Factors :Environmental Factors Crowding index: Easy spread from person to person through: Droplet spread Touching objects with flu viruses then touching mouth and nose Pass on the flu before sickness (1 day before symptoms) Speed of travel: Means of transport: World is becoming so small


Host :Host Lack of immunity: Antigenic shift: Pandemic General health and immune system of the individual Very high case fatality of the Avian Influenza: In animals: up to 100% In humans: up to 80% or even more


Human Pandemic Subtype :Human Pandemic Subtype Are we going to receive the vaccine on time? This depends on: Production time Transportation Country coordination with National and Regional WHO offices


Preventing the flu: get treated :Preventing the flu: get treated Tamiflu: Oseltamivir Work against influenza A & B viruses If taken 48 hours of becoming ill: Stops virus from bursting out of infected cells Used in children over 1 year of age WHO have advised all health authorities to stockpile anti-viral medicines to prepare for the pandemic.