Epidemics

  • Origen: An outbreak of an infectious disease that spreads quickly to many persons
    • PAN-demic: An epidemy that has spread over large areas and to many persons; normally declared by WHO
  • Trigger: Change in ecology in host population (stress and density of species), genetic or emerging pathogen.
    • Host immunity to a pathogen is below endemic equilibrium; infection starts
    • Transmission threshold is exceeded; infection starts
    • Normal reasons:
      • Increased virulence
      • Novel setting
      • Alteration in susceptibility
    • Behavior: Fast onset, everywhere and difficult to get away
    • Place: All areas, but in denser populated areas it is worse.
  • Other: It is difficult to predict potential risk, and estimate the onset
    • Do not need to be contagious
    • Might also be food related
    • Might be related to animals like mosquitos, flees and rats
    • Different types of outbreaks:
      • Point source outbreak: Where it starts; one place
      • Continuous outbreak: Variable exposure
      • Propagated outbreak: Person to person
    • Transmission:
      • Airborne transmission: Spread by droplet nuclei or dust in the air; normally 3-10 m
      • Arthropod transmission: Insect; mechanically or biologically
      • Biologically transmission: Involving a biological process
      • Colostral transmission: From generation to generation
      • Contact transmission: Directly from bites or droplets, water or liquids
      • Cyclopropagative transmission: The agent develops AND multiply in the process
      • Developmental transmission: The agent develops in the process
      • Fecal-oral transmission: From faces in host to the mouth of agent
      • Horizontal transmission: Spread to others in the same group
      • Mechanical transmission: Not invaded in tissue and the agent does not multiply
      • Propagative transmission: Agent multiplies I the transmission vehicle
      • Vertical transmission: Spreading in generations
    • Precaution:
      • Variation with seasons
      • Severity depends on periods; normally 5-10 year cycles
      • A biological event might easily kill an estimated 10.000.000 persons
    • Closedown of Society: Fast and long lasting; months

swineflu