Epidemiology, Healthcare

Class 3, 9/10

Strategies for Breaking Chain of Infection

• eliminate or contain reservoirs or pathogens

• prevent contact with infectious substances from exit pathways

• eliminate means of transmission

• block exposure to entry pathways

• reduce or eliminate susceptibility of potential hosts

Reservoirs of Infection

• where pathogens can multiply/survive until transferred to a host

• alive or inanimate

• living reservoirs: humans, animals/pets, insects, arachnids (ticks and mites)

  • may not experience illness caused by pathogens they harbor (carriers)

Zoonotic Diseases

• >60% of diseases originate in animals

• >2-0 known diseases that humans acquire from animal sources/living reservoirs

Categories of Zoonotic Diseases & Examples

• viral

  • avian flu

  • rabies

• bacterial

  • Lyme disease

  • plague

• fungal

  • ringworm/tinea

• protozoa

  • babesiosis

• helminth

  • dog tapeworm

Arthropods

• animals commonly associated with human infections/reservoirs

• insects (fleas, mosquitos, lice)

• arachnids (mites, ticks)

• considered “vectors” when they are involved in transmission of diseases

• examples:

  • ticks: Lyme disease

  • anopheles: malaria (mosquito)

  • flea: plage (80 species)

Non-Living Reservoirs of Infection

• air, soil, dust, contaminated water and foods, and fomites

• fomites: inanimate objects capable of transmitting pathogens

  • door handle, desk, phone, utensils, hospital bedding/towels/equipment

Modes of Transmission of Infectious Diseases

1. Contact

   • Direct

     • skin-skin

     • mucous membranes (kissing, sex)

   • Indirect

     • fomites

2. Droplet

   • >/= 5 micrometers in diameter

3. Airborne

   • evaporated droplet residue

   • <5 micrometers in diameter

4. Vehicular

   • contaminated objects (food, water, dust) by fecal matter

5. Vector

   • arthropods

Skin Infectious Diseases

• Route of Transmission/Entry:

  • skin discharge → air → respiratory tract

  • skin to skin

• Route of Exit:

  • skin

• Diseases:

  • chickenpox, colds, flu, measles, staph, and strep (skin discharge → air → respiratory tract)

  • impetigo, eczema, boils, warts, syphilis (skin to skin)

Respiratory Infectious Diseases

• Route of Transmission/Entry:

  • aerosol droplet inhalation

  • nose/mouth → hand/object → nose

• Route of Exit:

  • respiratory secretions

• Diseases:

  • colds, flue, pneumonia, mumps, measles, chickenpox, TB

Gastrointestinal Diseases

• Route of Transmission/Entry:

  • feces → hand → mouth

  • stool → soil, food, water → mouth

• Route of Exit:

  • Gastrointestinal secretions

• Diseases:

  • gastroenteritis, hepatitis, salmonellosis, shigellosis, typhoid fever, cholera, giardiasis, amebiases