Chain Of Infection Flashcards
Two basic principles of infection prevention and control is hygiene
Hand hygiene and environmental hygiene
Prudent antibiotic stewardship
“The right drug,for the right bug”
The traditional epidemiological triad models holds that infectious diseases result from the interaction of agent, host, and environment.
Chain of infection
3 parts of chain of infection
- Reservoir
- Mode of transmission
- Vector
The reservoir of an infectious agent is the habitat in which the agent normally lives, grows and multiples
Reservoir
Diseases that are transmitted from person to person without intermediaries
Human reservoir
Carriers commonly transmit disease because they do not realize they are infected, and consequently take no special precautious to prevent transmission
Human reservoir
Are those carriers who have recovered from their illness but remain capable of transmitting to others
Convalescent carriers (human reservoir)
Are those carriers who can transmit the agent during the incubation period before clinical illness begins
Incubatory carriers (human reservoir)
Those carriers who never experience symptoms despite being infected
Asymptomatic or passive or health carriers (human reservoir)
May or may not show the effects of illness
Human reservoirs
Are those carriers who continue to harbor to a pathogen such as hepatitis B virus or salmonella typhi
Chronic carriers (human reservoir)
Many of these disease are transmitted from animal to animal, with humans as incidental hosts
Animal reservoirs
Refers to an infectious disease that is transmissible under natural conditions from vertebrate animals to humans
Zoonosis
Ex. Of zoonosis
- brucellosis (cows and pigs)
- anthrax (sheep)
- plaque (rodents)
- trichinellosis/trichinosis (swine)
- Tularemia (rabbits)
- rabies (bats, raccoons, dogs, other mammals)
Plants, soild and water in the environment are also reservoirs for some infectious agents
Environmental reservoirs (fungal agents)
____ is the path by which a pathogen leaves its host
Portal of exit
Where does TB exits, schistosomes, cholera vibrios exits
Tb - respiratory tract
Sch - urine
Cholera - feces
portal of exit from the human reservoir includes
Blood
Open wound, needle puncture site
Any break in intact skin
RT
Sneezing, coughing, breathing, talking
GIT
mouth
Anus
Urine
Infectious agent may be transmitted from its natural reservoir to a susceptible host in different ways
Mode of transmission
Types of mode of transmission and its subtypes
Direct
1. Direct contract
2. Droplet spread
Indirect
1. Air borne
2. Vehicle borne
3. Vector borne (mechanical or biological)
An infectious agent is transferred from a reservoir to a susceptible hosts by direct contact or droplet spread
Direct transmission
A contact that occurs through skin to skin contract, kissing and sexual intercourse
Direct contact
Refers to spray with relatively large, short-range aerosols produced by sneezing, coughing or even talking
Droplet spread
Refers to the transfer of an infectious agent from a reservoir to a host by suspended air particles, inanimate objects (vehicles) or animate intermediaries (vectors)
Indirect transmission
Occurs when an infectious agents are carried by dust or droplet nuclei suspended in air
Airborne transmission
includes materials that has settled on surfaces and become re-suspended by air currents as well as infectious particles blown from the soil by the wind
Airborne dust
May indirectly transmit an infectious agent include food, water, biologic products, and fomites, objects such as handkerchiefs, bedding and surgical scalpels
Vehicles
a ___ may passively carry a pathogen
Vehicle
__ such as mosquitoes, fleas, and ticks may carry an infectious agent through purely mechanical means or may support growth changes in the agents
Vectors
Refers to the manner in which a pathogen enters a susceptible host
Portal of entry
Final link in the chain of infectious is a susceptible host
Host
Refers to the protective antibodies that are directed against a specific agent.
Specific immunity
Natural barriers to infection
Intact skin
Nasal cilia
Lung macrophages
Acidic environment in the stomach, urine and vaginal secretions
Tears that wash away pathogens
Saliva
Vehicleborne transmission may be interrupted by
Elimination or decontamination of the vehicle
How to rprevent airbore disease
Modifying ventilation or air pressure, filtering or treating the air
How to prevent oral-route transmission
Promoting hand washing
A way to interrupt vectorborne transmission
Controlling vector population. Spraying to reduce the mosquito population
Intervention to increase a host defenses
Vaccination
This concept suggests that if a high enough proportion of individuals in a population are resistant to an agent, then those few who are susceptible will be protected by the resistant majority since the pathogen will be unlikely to “find” those few susceptible individuals
Herd immunity
Susceptible hosts
Young children
Old individuals
Ppl with inadequate diets
Who are chronicaly ill
With open wounds
