Lecture 36: Outbreaks, Epidemics and Clusters

Question 1

How many stages are there that describe the epidemiological transition (changing pattern of disease)?

Answer 1

5

Question 2

Describe the epidemiological transition

Answer 2

The birth rate and death rate are high and the total population is low and then the death rate falls so population begins to increase and then birth rate falls and the total population keeps increasing and then plateaus

Question 3

What happens in stage one of the epidemiological transition?

Answer 3

birth rate and death rate are high

Question 4

What happens in stage 5 of the epidemiological transition?

Answer 4

birth rate is very low and death rate is low

Question 5

Where do high and low income countries sit in terms of stages on the epidemiological transition? Why is this?

Answer 5

High income countries are at level 5 because there is improved living conditions and low income countries are at level 1 due to infectious diseases and newborn and maternal problems due to inadequate care

Question 6

What does vector-borne mean?

Answer 6

infections coming from mosquitos

Question 7

What does zoonotic mean?

Answer 7

infections coming from other animals

Question 8

What are infections coming from other animals called?

Answer 8

zoonotic

Question 9

What is one health?

Answer 9

The interaction between human, animals and the environment and how we can work better with agriculturalists, vets, climate change people to improve health

Question 10

What 6 things influence the spread of disease?

• ______ of the agent
• _______ of infection
• biological _______
• ________ factors
• ________ variation
• ________

Answer 10

• properties of the agent
• sources of infection
• biological reservoirs
• host factors
• exposure variation
• environment

Question 11

One of the things that influences the spread of disease is the properties of the agent. What is meant by this?

Answer 11

how virulent it is, how it is transmitted, does it mutate

Question 12

One of the things that influences the spread of disease is the sources of infection. What is meant by this?

Answer 12

where does it come from - does it come from soil, water, insects, animals

Question 13

One of the things that influences the spread of disease is biological reservoirs. What is meant by this?

Answer 13

can it be present in an animal that don’t get infected, they just pass it on?

Question 14

One of the things that influences the spread of disease is host factors. What is meant by this?

Answer 14

is the host immunosuppressed, are they malnourished, or really healthy

Question 15

One of the things that influences the spread of disease is exposure variation. What is meant by this?

Answer 15

are people contracting the disease in a closed environment like a plane? it will spread faster if it is

Question 16

One of the things that influences the spread of disease is the environment. What is meant by this?

Answer 16

has climate change impacted the environment ie. is it warmer so mosquitos are more likely to be present

Question 17

What three things contribute to the epidemiological triangle and what three things do these make up?

Answer 17

1. the host
2. the agent
3. the environment
   - the host and the agent make up the transmission part of the triangle
   - the agent and the environment make up the survival part of the triangle
   - the host and the environment make up the immunity part of the triangle

Question 18

What is meant by the “host” in the epidemiological triangle?

Answer 18

descriptive epidemiology - describing data

Question 19

What is meant by the “agent” in the epidemiological triangle?

Answer 19

laboratory investigation - determining what the agent is

Question 20

What is meant by the “environment” in the epidemiological triangle?

Answer 20

environmental investigation into what caused the disease eg. rainfall

Question 21

What can we learn from the epidemiological triangle?

Answer 21

• what (agent)
• who (person/population)
• where (place)
• when (time)
• why/how (causes, risk factors and modes of transmission)

Question 22

What are some examples of infectious agents?

Answer 22

bacteria
viruses
fungi
protozoa
helminths (parasitic worms)

Question 23

Define infection

Answer 23

entry of a microbiological agent into a higher order host and its multiplication within the host

Question 24

Define infestation and give an example

Answer 24

multiplication of a microbial agent on (only) the surface of a higher order host and multiplication eg. lice

Question 25

Define infectivity

Answer 25

the ability of an organism to invade and multiply in a host - defines the secondary attack rate

Question 26

Define pathogenicity

Answer 26

the ability of an organism to produce clinical symptoms and illness - defines the proportion of those exposed who get ill

Question 27

Define virulence

Answer 27

the ability of an organism to produce serious disease - defines the case-fatality rate

Question 28

What are the three modes of transmission?

Answer 28

- direct - indirect - airborne

Question 29

What is meant by direct transmission of disease?

Answer 29

touching or inhaling infectious secretions such as saliva, respiratory droplets, urine, faeces, other body fluids

Question 30

What is meant by indirect transmission of disease?

Answer 30

it always involves either another object which can either be inanimate such as bedding, clothes, utensils, food, water, soil; or live via a vector such as mosquitos or ticks

Question 31

What is meant by airborne transmission of disease?

Answer 31

droplet nuclei travel in the air

Question 32

What are the three parts to the infectious process?

Answer 32

- the incubation period - the clinical period/the disease period - the recovery period

Question 33

What is meant by the latent part of the infectious process?

Answer 33

when you are infected but you can't spread the disease

Question 34

What is meant by the infectious period of the infectious process?

Answer 34

This is before the symptoms begin and it stops before you have recovered. This spans both the incubation period and the recovery period

Question 35

When are you most infectious?

Answer 35

in the first few days after developing the disease

Question 36

Define an outbreak/epidemic

Answer 36

An unexpected rise in the incidence of a disease - this can be limited to a localised increase in the incidence of disease or rising in an area that had no cases for a long time, This can also be defined as two or more cases identified from a common source or cases in excess of the expected number in a given time or place

Question 37

Define endemic

Answer 37

the constant presence of a disease or infectious agent within a geographical area or population group

Question 38

What are two types of endemic? Define them and state who is mainly affected

Answer 38

- holoendemic - intense diseases all year round, children mainly affected, most adults immune - hyperendemic - intense disease with time periods of no transmission such as during the dry season, persistent diseases with all ages infected

Question 39

Define pandemic

Answer 39

when a disease affects a large number of people and crosses many international boundaries

Question 40

Infections are often reported in clusters. Define clusters

Answer 40

an aggregation of relatively uncommon events or disease in space and/or time that are though to be greater than could be expected by chance

Question 41

What sort of diseases are usually reported as clusters?

Answer 41

rare non-infectious diseases such as HIV/AIDS

Question 42

Define primary case

Answer 42

the first case

Question 43

Define index case

Answer 43

the first case that is recognised by the health organisations

Question 44

What is the secondary attack rate?

Answer 44

the transmission or spread from the initial case

Question 45

Define R0

Answer 45

how many people will one person spread the disease to

Question 46

Who recognises an outbreak? (6)

Answer 46

- members of the community - media - clinicians - local public health agencies - national public health agencies - academic organisations

Question 47

Why do we need to investigate outbreaks? (6) - to ______ and ______ further illness - to prevent further ________ from other similar _______ - to address _______ ______ and involve the _____ in disease _______ - to reduce _______ and _________ costs - to identify new mechanisms of ________ of known ________ - to identify new or emerging _________ agents

Answer 47

- to stop and prevent further illness - to prevent further outbreaks from other similar sources - to address public concerns and involve the public in disease control - to reduce direct and indirect costs - to identify new mechanisms of transmission of known diseases - to identify new or emerging disease agents

Question 48

What are the 8 outbreak investigation steps?

Answer 48

- preparation - surveillance - confirmation - outbreak description - outbreak investigation - outbreak control - outbreak communication - outbreak documentation

Question 49

What are three parts to the outbreak investigation?

Answer 49

- analytic epidemiology component - environmental component - laboratory component

Question 50

What three things describe an outbreak?

Answer 50

the person (who), the place (where) and the time (when)

Question 51

What are the three types of outbreaks?

Answer 51

- common source - propagated source - mixed

Question 52

What are the three types of common source outbreaks? Give an example for each

Answer 52

- point source (eg. from a common event such as all the cases attended the same wedding - continuous common source (eg. continually contaminated water supply) - intermittent source (eg. only contaminated water supply after heavy rainfall)

Question 53

Give an example of propagated source outbreaks

Answer 53

person to person such as within a household or institution

Question 54

What is meant by mixed outbreaks?

Answer 54

point source then propagated person to person

Question 55

What does an epidemic curve graph?

Answer 55

the number of cases of a disease over time

Question 56

What does a common (point) source epidemic curve look like and why?

Answer 56

it is bell shaped because not everyone exposed at the same time gets unwell at the same time

Question 57

What does a continuous) source epidemic curve look like and why?

Answer 57

constant high cases over time because the infectious disease is not identified and people and people continue to get sick

Question 58

What does an intermittent source epidemic curve look like?

Answer 58

small groups of cases with blocks of no cases intermittently

Question 59

What does a propagated source epidemic curve look like?

Answer 59

one case and then more cases and then lots of cases because one case spreads it to people who spread it to more people and then they spread it to more people

Question 60

What is the plan for pandemics?

Answer 60

- plan for it - keep it out - stamp it out - manage it - recover from it

Question 61

One of the steps to managing pandemics is to keep it out. What is meant by this?

Answer 61

border control, preparation, communication, surveillance, self-isolation

Question 62

One of the steps to managing pandemics is to stamp it out. What is meant by this?

Answer 62

early recognition, case finding, contact tracing and isolation

Question 63

One of the steps to managing pandemics is manage it. What is meant by this?

Answer 63

delay the increase by infection control, triage, treatment, closure of institutions, bracing the health system and the public