Communicable diseases:

Question 1

infectious disease:

Answer 1

A microorganism that has the potential to cause Illness on a wide scale due to its propensity for transmissibility, which is an inherent part of its reproductive cycle

Question 2

communicable disease:

Answer 2

A microorganism that has the potential to cause Illness, and which is transmittable to other host organisms (people in this case)

Question 3

Endemic:

Answer 3

– An incidence of disease that has a reasonably high yet approximately constant infection rate within a particular
population (e.g. annual cold/flu)

Question 4

Epidemic:

Answer 4

– An endemic that for opportunistic reasons (weather, flood, starvation, war, pestilence), exceeds the normal number of
infections in a population (e.g. ebola in Africa, 2013-14

Question 5

Pandemic:

Answer 5

– A global or intercontinental incidence of

disease (e.g. Spanish Flu in 1918-1

Question 6

Bubonic Plague:

Answer 6

The extent of later outbreaks of 
Bubonic Plague were such that in 
Naples (1656) an enormous city of 
500,000 saw approx. 300,000 deaths.
There were not enough inhabitants to 
actually bury the dead
• 60,000 bodies were 
burned  
• 100,000 were simply 
dumped into the sea
• Stench of decomposition in the city 
• Dogs, vultures and rodents
• Law-and-order and social chaos

Question 7

catalyst for Change

Answer 7

• How did our approach change to 
diseases and viruses
• Austin Bradford Hill –English 
Epidemiologist (1950’s)
• Linked ‘smoking to lung disease’
• Casual Association

Question 8

bradford Hill criteria for causality:

Answer 8

Strength: The greater the association the greater the strength. ? Small
association

Consistency: consistent findings in different persons, places and times
increases the likelihood of association

Specific :The more specific an illness to a specific population, the greater the
probability of causality

Temporal: temporal sequence – the outcome of interest has to occur after the
exposure

Biological gradient :Greater the exposure, the greater the effect

Plausibility: the association has to make biological sense consistent with current knowledge

Coherence: Coherence between field experimentation and laboratory findings

Experiment :Occasionally it is possible to appeal to experimental evidence

Question 9

Changes in Medical Thinking:

Answer 9

Development of Public health strategies:
• Quarantine
• Sanitation
• Urban clean ups
• Magic bullets – quinine, penicillin, antibiotics
• Concealment: China and SARS – Naples and cholera
Ethical issues of human experimentation

Question 10

important People in the history of

Communicable Diseases:

Answer 10

Edward Jenner
• The ‘Jennerian approach to vaccination’
• The father of immunology.

John Snow (no, the other one)
• Hypothesis that disease (cholera) was being transmitted by water and not poisonous vapour
•The father of epidemiology

Louis Pasteur
• Famous for ‘pasteurization’

Question 11

portal of exit:

Answer 11

How pathogenic agent leaves infected host to invade another. This is agent dependent:
- Genitourinary Tract/Reproductive Systems
- Gastrointestinal tract
- Respiratory Tract
- Skin – Via open wound/lacerations or through
bites

Question 12

Modes of Transmission:

Answer 12

Direct Contact
– touching an infected person including sexual contact

Indirect Contact
– touching contaminated surfaces

Food or Waterborne
- ingestion of food or water contaminated
with pathogenic agent. Often these infections are also spread by the faecal-oral route.

Airborne
– droplets from speech, coughing, sneezing or those

Question 13

susceptibility to Communicable

Diseases:

Answer 13

Is influence by your immune response but also impacted on 
by:
- Age
- General Health Status
- Immune Status
- Cultural Behaviours
- Sexual Behaviours
- Environmental and Geographical conditions

Question 14

Nosocomial infections:

Answer 14

Nosocomial infections (healthcare associated infections)
Consider:
• Why people get such infections
• Why traditional infection control is failing
The nature of nosocomial infection is such that 5-7% of admissions to a
teaching hospital acquire an infection that they did not have prior to admission
• Predominant infections:
• Catheter associated urinary tract infections
• Surgical wound infections
• Pneumonia

Question 15

Nosocomial infections:

Answer 15

The incidence of nosocomial infections are such that trauma victims who actually
arrive at hospital alive have a significantly high relative risk of hospital acquired
infection
• Ventilation associated pneumonia
• Urosepsis – urinary catheter
• Bacteremia – central line
• Surgical MRSA

Question 16

Nosocomial infections:

Answer 16

Rates of nosocomial infections in ICU are 3-5 times higher than
any other clinical environment
Rates of bacteremia in the ICU are 10 times higher
• Swedish hospitals are some of the most aseptic clinical environments
• Prevalence survey of 60 Swedish hospitals found that the rate of ICU
acquired infections were 33%
• A similar prevalence survey in Canada found over 50% of ICU patients
developed a Hospital Acquired Infection (HAI)
• Infections acquired in ICU result in:
• Extremely high mortality risk
• Lengthened hospital stay
• Increased burden on the healthcare infrastructure