Session 3 - Communicable Disease Control

Question 1

What is the definition of public health?

Answer 1

The science and art of preventing disease, prolonging life and promoting health through the organised efforts of society.

Question 2

What is the definition of health protection?

Answer 2

The protection of individuals, groups and populations through expert advice and effective collaboration to prevent and mitigate the impact of infectious disease; environmental, chemical and radiological threats.

Question 3

What are the 3 domains of health protection?
Explain them.

Answer 3

Communicable disease control - prevention, investigation, control and management of infections.

Environmental public health - identification of and the response to threats from the environment.

Emergency preparedness, resilience and response - preparation, prevention and recovery from events that threaten serious damage to human welfare.

Question 4

What are some factors that are of increasing relevance for health protection requirements?

Answer 4

Climate - extreme weather.
Population density - disease types and spread.
International travel - outbreaks and pandemics.
New diseases - zoonotic.
Geopolitical conflicts - wars and refugees.

Question 5

What do people of health protection work to prevent or resolve?

Answer 5

Infectious disease outbreaks - plagues.
Environmental hazards - floods, storms and droughts.
Man-made hazards - wars, fires and the built environment.

Question 6

What is the epidemiological triangle model?

Answer 6

Host - the case, infected person, or asymptomatic carrier.
Agent - the pathogen or substance of concern.
Environment - the place in which transmission can occur, including sanitary conditions, the social context and access to healthcare.

Question 7

What is the chain of infection model?

Answer 7

An infectious agent can:
- sit in a reservoir of the agent, or
- transmit to the susceptible host via the portal of entry.
The agent then leaves the host via the portal of exit.
The agent spreads via a mode of transmission.

Question 8

What are the 5 main modes of disease transmission?

Answer 8

Inhalation/ aerosol or droplet.
Ingestion/ faecal-oral.
Direct contact.
Vector.
Blood-borne.

Question 9

Explain how we eradicate an infectious hazard via the source-pathway-receptor model.

Answer 9

Breaking the chain.

Source - remove the source, kill/ inactivate the pathogen or isolate the patient.

Pathway - barriers to the receptor (PPE), education to prevent the transmission route, behaviour modification, or procedural measures like cooking.

Receptor - removing, relocating or rerouting a population; protecting a population (immunisation, chemoprophylaxis).

Question 10

What is vehicle borne transmission and the two different types of vector-borne transmission?

Answer 10

Vehicle - transmission through an inanimate object.

Vector borne:
- mechanical; sticking to the vector.
- biological; living in the vector.

Question 11

What are the 3 different definitions of an outbreak?

Answer 11

Two or more cases of an infectious disease, that are linked by time, place or person.

An increase in cases of an infectious disease, over and above the normal background rate of the disease.

Any case of an infectious disease that does not normally occur in that setting.

Question 12

What is a cluster?

Answer 12

An aggregation of cases that may be epidemiologically linked, or not.
They often need further investigation to determine if they are an outbreak or not, as they often arise randomly.

Question 13

What are the 3 types of epidemic curves?

Answer 13

Point source - a tight spike of cases followed by decay.

Propagated - several discrete spikes of cases, often due to an incubation period.

Extended - a continuous, common source of cases.

Question 14

What is the R number?

Answer 14

The reproductive number of a disease, a measure of transmission potential - the expected number of secondary cases for each primary case.

Question 15

What is the R0?

Answer 15

The basic reproductive number of a disease, to a completely susceptible population.

Question 16

What is the Re?

Answer 16

The effective reproductive number.

Question 17

What is sensitivity and how can we calculate it?

Answer 17

How good a test is at correctly identifying the presence of disease.

True positive / (True positive + False negative).

Question 18

What is specificity and how can we calculate it?

Answer 18

How good a test is at correctly identifying the absence of the disease.

True negative / (True negative + False positive).

Question 19

What is the positive predictive value and how can we calculate it?

Answer 19

How likely a positive result is to be true.

True positive / (True positive + False positive).

Question 20

What is the negative predictive value and how can we calculate it?

Answer 20

How likely a negative result is to be true.

True negative / (True negative + False negative).

Question 21

What is surveillance of an outbreak?

Answer 21

An ongoing gathering, analysis and interpretation of data about disease incidence and prevalence, with timely dissemination.

Question 22

What are the aims of managing an outbreak?

Answer 22

Controlling the spread of a disease.
Limiting morbidity and mortality.
Developing preventative strategies.
Evaluating and refining existing measures.
Improving knowledge of new and existing diseases.
Addressing public concern.

Question 23

What are some factors to consider when managing an outbreak?

Answer 23

The context and setting.
The public concern.
How clinically severe it is.
Transmissibility of the disease.
Wider risks.

Question 24

What are the 6 steps to managing an outbreak?

Answer 24

Assembling a team.
Verifying the outbreak.
Finding cases.
Develop/ test the hypothesis.
Implement control measures.
Communicate findings.

Question 25

What is required for case definition?

Answer 25

Consistency and precision to defining an outbreak.
Appropriate sensitivity and specificity of a test, or utilisation of signs/ symptoms.
Pragmatism.

Question 26

What are the factors of descriptive epidemiology?

Answer 26

Demographics.
Time - onset dates.
Place - travel and possible exposure places.
Clinical symptoms and vaccination history.
Social and behavioural factors.

Question 27

What study should be performed when managing an outbreak and why?

Answer 27

A case-control study - cases are identified and causative factors can be found to help prevent further transmission.

Question 28

What is the definition of an emergency, according to the civil contingencies act?

Answer 28

An event, situation, war or terrorism which threatens serious damage to human welfare, environment or security.

Question 29

What are the categories of emergency planning?

Answer 29

Anticipation.
Assessment.
Prevention.
Preparation.
Response.
Recovery.

Question 30

What are the 5 steps of evidence based medicine?

Answer 30

Formulating an answerable clinical question.
Finding evidence.
Appraising the evidence.
Applying the evidence.
Evaluating performance.

Question 31

What are the definition of evidence based medicine?

Answer 31

The integration of best research evidence with clinical expertise and patient values.

Question 32

How can an answerable clinical question be formed?

Answer 32

PICO:
- Population.
- Intervention.
- Comparison.
- Outcome.

Question 33

What is the purpose of surveillance?

Answer 33

• Identify individual cases of disease.
• Measuring the incidence of infectious disease.
• Tracking changes in occurrence and risk of an infectious disease.
• Evaluating existing control measures.
• Identifying new emerging infections of health importance.

Question 34

What is syndromic and sentinel surveillance?

Answer 34

Syndromic - looking for symptoms.
Sentinel - testing with specific sampling strategies.

Question 35

What is passive and active surveillance?

Answer 35

Passive - a designated body that receives reports of infectious disease or illness submitted from hospitals, GP surgeries or public health units.

Active - a system where a member from public health England contacts healthcare providers to seek information about certain conditions.

Question 36

What is routine and enhanced surveillance?

Answer 36

Routine - collection of minimum data set.

Enhanced - collection of more detailed data sets from informants.

Question 37

What are the limitations of surveillance?

Answer 37

Underreporting.
Lack of representatives - less serious illnesses, usually.
Lack of denominators - unknown which populations are at risk.
Trends are difficult to interpret as sensitive to changes in testing or reporting by laboratories.

Question 38

What is an index and secondary case?

Answer 38

Index - the first case to come to the attention of an investigator, not always the primary case.

Secondary - the case that contracted the infection from the primary case.