Infection Process

Question 1

Define the infection process?

Answer 1

The lifecycle process of how an infection affects a person after a pathogen enters the body

Question 2

What are the five stages of the infection process?

Answer 2

Incubation
Prodromal
Illness
Decline
Convalescence

Question 3

What is the incubation phase?

Answer 3

Time from exposure to onset of non-characteristic symptoms
Microbe is multiplying

Question 4

What is the prodromal phase?

Answer 4

Time between incubation and the onset of characteristic symptoms
Microbes are multiplying
Host is infectious
Immune response starts so non-specific symptoms begin

Question 5

What is the illness phase?

Answer 5

Host has characteristic symptoms
Host is infectious

Question 6

What is the decline phase?

Answer 6

Immune response starts to win and reduce the number of microbes
Symptoms start to improve
Secondary infection possible due to weakened immune response
Host still infectious

Question 7

What is the convalescence phase?

Answer 7

Symptoms resolve and normal function resumes

Question 8

What is a ‘carrier’?

Answer 8

A person who is colonised with a pathogen but does not show symptoms

Question 9

Define the chain of infection

Answer 9

Steps that are required in order for a new host to become infected
All 6 links must exist in order for infection to occur

Question 10

What are the 6 links in the chain of infection?

Answer 10

Causative agent
Reservoir
Portal of exit
Mode of transmission
Portal of entry
Susceptible host

Question 11

What is the reservoir in the chain of infection?

Answer 11

A habitat for the pathogen to live/grow in
Human, animal or environment

Question 12

What is the portal of exit in the chain of infection?

Answer 12

How the pathogen leaves its habitat/host
Usually via the same site where it has localised (e.g. flu localised in respiratory tract leaves via cough/sneeze)

Question 13

What is the mode of transmission in the chain of infection?

Answer 13

How the pathogen is transferred from source to host
Contact, droplet and/or airborne

Question 14

What is contact mode of transmission?

Answer 14

Directly when a new host touches the contaminant source (host touches host)
Indirectly when a host touches some contaminant on an intermediary object. This can be a vector where a living organism transfers the pathogen (e.g. mosquito) or a vehicle where a substance carries the disease (e.g. soil)

Question 15

What is droplet mode of transmission?

Answer 15

Particles >5 micron
Limited by force vs. gravity
Usually <1m

Question 16

What is airborne mode of transmission?

Answer 16

Often <5micron particle
Remain infective over long distances and time
Created by talking, coughing etc and the evaporation of droplet

Question 17

What is the portal of entry in the chain of infection?

Answer 17

How the pathogen enters the new host
E.g. injury to skin, ingested, inhaled

Question 18

What is the susceptible host in the chain of infection?

Answer 18

There must be a new host who gets colonised by the pathogen