Describe the infectious disease process

Infectious disease agent 

• Typically microorganisms e.g. bacteria, fungi, parasites

Reservoir

• Normal habitat where the agent lives and multiplies 
• E.g. rabies is dogs not humans
• 4 types or carriers 
  • Systematic cases/carries 
  • Human carriers types 
    • Incubatory = transmit infectious agent before symptoms begin  
    • Inapparent = transmit infection without ever getting it themselves e.g. polo 
    • Convalescent = received from infectious but can still infect others
    • Chronic = received from illness but can harbour infection for months/years 
  • Animal 
  • Insects 
  • Environments 

Portal of exit

• Any route that allows pathogen to leave host
  • Alimentary e.g vomiting
  • Genitourinary
  • Respiratory 
  • Skin
  • Trans placental

Mode of transmission 

• Direct transmission
  • instantaneous
• Indirect transmission 
  • Not direct human to human interaction 
  • Caused by flies, water, mosquito, airborne etc. 

Portal of entry

• Tool by which infection can enter suspectable host
  • Inhalation 
  • Absorption
  • Ingestion
  • Inoculation
  • Introduction 

Host susceptibility

• Depends on variety of factors
  • Age, gender, lifestyle, medical history, heredity, host physical barriers