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