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  1. 1. Influenza Ieuan Davies
  2. 2. Signs and Symptoms <ul><li>Influenza is an acute, viral respiratory infection. </li></ul><ul><li>Fever, chills, headache, aches and pains throughout the body, sore throat which may lead to bronchitis or pneumonia. </li></ul><ul><li>Vomiting and diarrhoea may also occur. </li></ul><ul><li>Many deaths have been attributed to influenza </li></ul>
  3. 3. Influenza Pandemics <ul><li>A pandemic is a world wide spread of infection occurring in many countries simultaneously. </li></ul><ul><li>Flu pandemics occur approximately every thirty years. </li></ul><ul><li>Flu pandemics occur because a new strain of the virus emerges for which people have no immunity and there are no vaccines available. </li></ul>
  4. 4. Pandemics <ul><li>New flu viruses occur due to mutation </li></ul><ul><li>Mutation occurs because different strains of influenza virus can exchange genes by infecting different animals </li></ul><ul><li>Avian influenza viruses can exchange genes with human influenza viruses creating hybrid strains </li></ul>
  5. 5. 1918 - 1919 pandemic <ul><li>This killed between 20 – 40 million people </li></ul><ul><li>Face masks were worn but provided little protection against infection </li></ul>
  6. 6. Cause <ul><li>The cause of influenza is the influenza virus. </li></ul><ul><li>Influenza A, B and C viruses are found </li></ul><ul><li>Influenza A viruses are associated with serious illness and pandemics </li></ul>
  7. 7. Influenza virus <ul><li>The flu virus is an RNA virus </li></ul><ul><li>The genome codes for five viral proteins and is made of eight fragments. </li></ul><ul><li>The virus has a lipid envelope with two glycoproteins present </li></ul>
  8. 8. Flu virus glycoproteins <ul><li>Haemagglutinin - this glycoprotein plays a part in infection and provides the “H” in the strain type. </li></ul><ul><li>Haemagglutinin attaches the virus to cells and allows the viral envelope to fuse with the cell membrane and enter cells. </li></ul><ul><li>Neuraminidase – has a mushroom shape, its role is to allow the release of viruses to infect other cells </li></ul>
  9. 9. HN terminolgy <ul><li>H refers to Haemagglutinin types and each is given a number H1, H2 etc, </li></ul><ul><li>Neuraminidase is designated N and different forms are available as well e.g. H5N1 (avian) and H1N1. </li></ul><ul><li>Different combinations of H and N glycoproteins give rise to different strains </li></ul>
  10. 10. Antigenic shift and antigenic drift <ul><li>Mutations which produce small changes in antigens are referred to as antigenic drift and these occur in the same strain </li></ul><ul><li>Mutations which result in a major change and produce new strains are referred to as antigenic shifts </li></ul>
  11. 11. Life cycle of the ‘flu virus
  12. 12. Transmission <ul><li>The virus is spread by inhalation or by direct contact. </li></ul><ul><li>Reservoirs of infection are primarily humans, but birds and pigs can act as reservoirs. </li></ul><ul><li>The multiple host status makes for mixing of flu types. </li></ul>
  13. 13. Prevention <ul><li>Public education campaigns are used to reduce infection rates </li></ul><ul><li>Isolation of infected people is desirable but not always practical </li></ul><ul><li>Immunisation </li></ul>
  14. 14. Immunisation <ul><li>Vaccines are offered to people aged 65 or over ( Note: Currently this group has some immunity and are not being targeted ) </li></ul><ul><li>Clinically at risk groups – asthmatics, immuno-compromised patients, diabetics, people with chronic respiratory disease. </li></ul><ul><li>Health care workers </li></ul><ul><li>Vaccine effectiveness varies between 40 – 60% </li></ul>
  15. 15. Chemotherapy <ul><li>Tamiflu (oseltamivir) – inhibits the neuraminidase and thus prevents the spread of the virus in the body </li></ul><ul><li>Tamiflu can therefore be used to reduce the length of illness and its transmission within a household </li></ul><ul><li>Resistance of H1N1 strain to oseltamivir has been reported at 25% </li></ul>
  16. 16. Conclusion <ul><li>Flu can be a bit of a swine! </li></ul><ul><li>Prevention is better than cure! </li></ul><ul><li>Avoid contact with infected people. </li></ul><ul><li>Read how the population of Eyam avoided spreading the plague! </li></ul><ul><li>Eyam - Plague Village - Derbyshire </li></ul>
  17. 17. This powerpoint was kindly donated to Is home to well over a thousand powerpoints submitted by teachers. This a free site. Please visit and I hope it will help in your teaching