Epidemiology and Spread of Infectious Disease (L38)

Question 1

what are the sources of infection for humans? (3)

Answer 1

• animal reservoirs (zoonotic disease)
• non-living reservoirs
• human carriers/cases
• nosocomial infection

Question 2

what is the term for when there is an animal reservoir of disease?

Answer 2

zoonotic disease

Question 3

what are some examples of zoonotic diseases?

Answer 3

rabies, anthrax, ringworm, giardia

Question 4

what are fomites?

Answer 4

physical objects which become infected and can transmit infection to humans

Question 5

how can infection be transmitted?

Answer 5

• contact: direct, indirect, droplet

- vectors: mechanical, biological

Question 6

what are the 5 stages of an infectious disease?

Answer 6

• incubation period
• prodromal period
• illness
• decline
• convalescence

Question 7

what occurs during the incubation period?

Answer 7

• individual has been exposed to the organism which is growing in tissues
• showing no signs or symptoms

Question 8

how long does the incubation period last for and what determines this length of time?

Answer 8

may take a short or long time
depends on:
- virulence
- dose
-immune defences
- pathogen characteristics
- site of infection

Question 9

what occurs during the prodromal period?

Answer 9

• show vague, general symptoms

- symptoms are non-specific and if infectious during this stage, may spread disease before you know you have it

Question 10

why is the prodromal period an important stage of infectious disease?

Answer 10

because treatment during this stage may intercept the development of the disease
also may be important for differential diagnosis

Question 11

what is the illness stage of infectious disease?

Answer 11

• the stage where the most characteristic signs and symptoms of the disease are evident
• most infectious stage

Question 12

what is the decline stage of infectious disease?

Answer 12

• when immune response or medical intervention resolves infection which leads to decrease in pathogen numbers -> declining signs and symptoms
• immune parameters peak

Question 13

what occurs during the convalescence period of infectious disease?

Answer 13

• no signs or symptoms

- tissues repaired as recovering from damage caused by infectious organism

Question 14

what does the time period of convalescence depend on?

Answer 14

• amount of damage
• nature of pathogen
• infection site (CNS = lifelong effects)
• patient health and immune competence

Question 15

what are nosocomial infections?

Answer 15

infections that occur in health care facilities

Question 16

what are the types of nosocomial infection?

Answer 16

• exogenous
• endogenous
• iatrogenic

Question 17

what are exogenous nosocomial infections caused by?

Answer 17

infection from someone else

Question 18

what are endogenous nosocomial infections caused by?

Answer 18

infection from opportunistic pathogens on own body due to catheters (tubes inserted into body)

Question 19

what are iatrogenic nosocomial infections caused by?

Answer 19

infection from someone else due to not using sterile instruments or washing hands

Question 20

what are the 3 ways in which infectious diseases can be classified?

Answer 20

• body system
• taxonomic group
• longevity and severity

Question 21

what are the categories within the infectious disease classification of longevity and severity?

Answer 21

- acute
will start and end within days
will either die or get better
- chronic
go on for months or years
- subacute
largely secondary infections
- latent

Question 22

what are some examples of all the categories within the infectious disease classification of longevity and severity?

Answer 22

- acute
common cold
- chronic
TB
- subacute
subacute endocarditis
- latent
chicken pox -> shingles, herpes

Question 23

what does it mean if a disease is epidemic?

Answer 23

occurs in a large number of people in a population at the same time

Question 24

what does it mean if a disease is pandemic?

Answer 24

disease is widespread, usually worldwide

Question 25

what does is mean if a disease is endemic?

Answer 25

the disease is constantly present in a population, usually at low incidences

Question 26

what does it mean if a disease is sporadic?

Answer 26

disease only occurs in a few scattered cases

Question 27

outline the experimental approach to epidemiology studies (4)

Answer 27

- reporting of clinical cases attending hospitals or medical practices - diagnostic follow up to confirm disease incidence/prevalence - monitor disease incidence following therapy/vaccination - monitor case histories/patient records