principals of infectious diseases

Question 1

What are the levels of infection

Answer 1

Colonistation
subclinical infection
latent infection
clinical infection

Question 2

What is a communicable disease

Answer 2

Capable of being directly or indirectly transmitte from n infecte person to another, or from animal to human or from environment to human

Question 3

What are the three points in an epidemiological triad of disease transmission

Answer 3

Host
agent
environment

Question 4

What are the different modes of transmission

Answer 4

Direct- contact HIV/STI’s
Contact with soil -helminths
inoculation into skin/mucosa -schitosomiasis
Transplacental- syphilis rubella

Indirect
vehicle-borne - food water (salmonella, shigella, chlorea)
Vector borne- malaria, dengue
Airborn-measels
fomite born- scabies
Unclean hands and fingers
Droplet infection TB

Question 5

What is the iceberg concept of infection

Answer 5

Clinical perception is only of those who have reached the symptomatic period but there may be many more subclinically in

Question 6

How is the rate of transmission measured

Answer 6

Basic reproductive number
the mean number of individuals directly infected by an infectious case throughout the total infectious period, when introduced to a susceptible pop

Question 7

What is the equation for R0

Answer 7

P=probability of transmission per contact
C= contacts per unit time
D= duration of infectiousness
PxCxD

Question 8

What is R>1

Answer 8

The infection will become epidemic

Question 9

What if R=1

Answer 9

The infection will become endmeic

Question 10

Define endemic

Answer 10

Persistent occurance/prevalence with low to moderate levels at all time (STI)

Question 11

Define epidemic

Answer 11

sudden occurance clearly in excess of expected for a given pop at a given time

Question 12

Explain herd immunity

Answer 12

form of immunity that occurs when the vaccination of a significant portion of a pop provides a measure of protection for individuals who have not developed immunity

Question 13

How can R0 be used to with herd immunity

Answer 13

helps calculate the lowest percentage of people need to be immune to prevent epidmeics
the higher the R0 value the higher proportion needed to be immunized

Question 14

When is a disease outbreak labeled as an epidemic

Answer 14

Sharp rise in cases of an endemic disease (malaria)
just one confirmed case of a non-endemic disease (cholera)
1 suspected case of a highly fatal case (ebola)
5 or more suspected cases or at least 3 confrimed cases of measels

Question 15

Define eradication and suggest a disease to which this is applicable

Answer 15

Eradication it the termination of all transmission of the infectious agent through survellance and containment, none in the world= small pox

Question 16

Define elimination and an example of a disease that has been eliminated

Answer 16

Eradication from a large geographic region. Polio measels and diptheria, tetanus, whooping cough, yellow fever

Question 17

Define hyper endemic

Answer 17

equally endemic in all age groups

Question 18

Define holoendemic

Answer 18

children more than adults

Question 19

define a pandemic

Answer 19

widespread epidemic distribute or occuring throughout a region/country/continent/glabally

Question 20

Define point source outbreak

Answer 20

Point source- same exposure over a limited define period of time, usually within one incubation period, rapid rise, peak and then gradual fall

Question 21

Definecommon persistent source outbreak

Answer 21

exposure to source prolonged and may occur over more than 1 incubation period eg malaria

Question 22

Define common intermittent source outbreak

Answer 22

sporadic cases of any disease

Question 23

Define propagated progressive source outbreak

Answer 23

case of disease serves as sources for later cases, series of sucessively larger peaks,reflective of increasing numbers of cases caused by person to person contact

Question 24

An outbreak has been confirmed what are the two routes of action

Answer 24

Immediate control measure

further investigations

Question 25

Describe what immediate control measures are there in an outbreak

Answer 25

Prophylaxis
Exclusion/isolation
public warning
hygiene measures

Question 26

Describe what further investigations can be done when an outbreak has been identified

Answer 26

aetiological agent
mode fo transmission
vehical of tranmission
source of contamination
population at risk
exposure causing illness

Question 27

When the cause is know but the mode of tranmission isnt what is prioity

Answer 27

investigation

Question 28

When the cause is unknown but the source is known what is prioity

Answer 28

Both investigation and control equally important

Question 29

If the causative agent is unknown and so is the source of the transmission what is the priority

Answer 29

investigation

Question 30

What are the 10 steps n outbreak investigation

Answer 30

1prepare for field work
2confirm if it is an outbreak
3verify diagnosis and confirm disease
4define an identify case
5descriptive;orient data in terms of time place and person
6Interpret and develop hypothesis
7Analyse; evaluate hypotheses
8draw conclusions
9implement control and prevention measures
10communicate findings and write a report

Question 31

How do you identify cases in a outbreak investigation

Answer 31

based on timing and infection:
index=1st case
primary=case that brings infection into a pop
secondary=infected my primary case
based on degree of certainty:
possible/suspected, few features
probable- typical features no lab confirmation
confirmed

Question 32

What is the development of a line listing

Answer 32

Identifying info
demographic info
clinical info
risk factor info
reported info

Question 33

What is the role of the lab

Answer 33

confirm diagnosis
identify new pathogens
tracing spread through typing pathogen
antimicrobila susceptabilty as a guide to treatment
post-outbreak survellience

Question 34

How can the source, mode or vehicle of transmission be identified

Answer 34

geographical scope

Question 35

How can epidemic curves help us

Answer 35

helps understand
size of epidemic
relationship to endemics
pattern of spread
time course and where you are in the course

Question 36

How can a hypothesis be evaluated

Answer 36

Against facts, or using analytical epidemiology to quantify relationships and explore the role of chance

Question 37

What is the case fatality rate

Answer 37

the proportion of infected indivduals who die from the infection
deaths/diseased x 100

Question 38

What is the attack rate

Answer 38

proportion of non-immune exposed individuals who become clinically ill
ill/ill+well x100

Question 39

What is the incidence risk ratio

Answer 39

Compare the incidence risk of the disease in the exposed and unexposed groups,
incidence risk of a disk exposed/unexposed

Question 40

What is the odds ratio

Answer 40

Compare the odds of exposure in cases and controls odds of exposure in cases/odds of exposure in controls

Question 41

How can it be decided when the outbreak is over

Answer 41

Looking at
no.of suspected persons who are exposed to course and become infected
period of time over which suspetible people are exposed to the source
minimum and maximum incubation periods for the disease

Question 42

What usually indicates the outbreak is over

Answer 42

2 case free incubation periods

Question 43

Who are the stake holders

Answer 43

Outbreak investigation staff
ph personnel
government officials
healthcare providers
media
community

Question 44

What should the purpose of a final report be

Answer 44

communicate ph messages
influence policy
evaulate performance
training tool
legal proceedings