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