Influenza

• Influenza

  • A.k.a FLU
• Influenza Viruses : Family Orthomyxoviridae
• Influenza A

  • Epidemics and Pandemics
  • Infect humans, birds, pigs, horses, and seals.
  • Sources of new strains
• Influenza B

  • Epidemics
  • Only restricted to humans
• Influenza C

  • Infect humans but milder and less common
  • Not associated with widespread outbreaks or severe illnesses
• Antigenic Drift

  • Minor change caused by point mutations.
  • Amino acid changes in the hemagglutinin (HA) antigen.
  • Occurs in both Influenza A and B and is responsible for epidemics.
• Antigenic Shift

  • Major change of rearrangement of gene segments in the HA or neuraminidase (NA) antigen,
  • Occurs only in Influenza A and is responsible for pandemics.
• Avian Flu

  • Caused by a new strain called H5N1, which is closely monitored for uts pandemic potential.
• H5N1

  • Not a result of antigenic drift or shift and has existed since 1950s.
• 1919-1920

  • Spanish flu pandemic caused at least 20 million deaths.
• Mexican Swine Flu A(H1N1) Pandemic

  • Quadruple re–assortant virus resulting from the recombination of two strains from birds, one from swine and one from human.
• Asian Flu (1957) and the HongKong Flu (1968)

  • Killed more than 1.5 million people
• Mode  of Transmission

  • Respiratory Droplets
  • Direct Contact
  • Indirect Contact
  • Airborne Contact
  • Airborne Transmission
• Pathogenesis


  1. Entry and Attachment

  2. Replication and Spread

  3. Destruction of Epithelial Cells

  4. Immune Response

  5. Inflammatory Response

  6. Clearance of the Virus
• Entry and Attachment


  Influenza viruses primarily enter the body through inhalation of respiratory droplets containing the virus
• Replication and Spread


  The influenza virus enters the host cells and replicates, leading to the production of new viral particles
• Destruction of Epithelial Cells


  Viral replication and release cause damage to the respiratory epithelial cells
• Immune Response


  It recognizes the presence of the virus and triggers an immune response
• Inflammatory Response


  Results in the release of cytokines and chemokines, which attract immune cells to the site of infection
• Clearance of the Virus


  It works to clear the influenza virus from the body
• Uncomplicated Influenza

  • Symptoms: chills, headache, and dry cough.
  • Followed by: high fever, generalized muscular joints, malaise, anorexia.,
• Rye’s Syndrome

  • Associated with Influenza B and varicella zoster infections.
  • An acute encephalopathy that occurs in children and adolescents and is associated with the intake of aspirin or salicylate.
• These are not recommended to treat influenza

  • Aspirin
  • Corticosteroids
• Unactivated Influenza Vaccine

  • Dead virus
  • Injection
  • Best choice
• Live Attentuated influenza Vaccine

  • Live, wekaned virus
  • Intranasal
  • Should be given to people who cannot take the shot
  • Health for people ages 2 to 49 years old who are not pregnant.
  • Should not be given to anyone who has a weak immune system.