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Epidemiology > Principles Of Epidemiology > Flashcards

Principles Of Epidemiology Flashcards

1
Q

What is the purpose of epidemiology

A

To obtain, interpret and use health information to promote health and reduce diseases

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2
Q

What’s re the four phases in the use of epidemiological approach

A

Descriptive epidemiology
•Analytical epidemiology
•Intervention or experimental epidemiology
•Evaluation epidemiology

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3
Q 
Which use of epidemiological approach is concerned with the Concerned with disease distribution and frequency
•Ask
–What
•Problem
•Frequency
–Who
–Where
–When
A

Descriptive

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4
Q

Which use of epidemiological approach is concerned with Analysing the causes, or determinants of diseases by testing hypothesis
•Answer questions such as
–How is the disease caused?
–Why is it continuing ?

A

Analytical epidemiology

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5
Q

What is intervention or experimental epidemiology

A

Clinical and community trials to check for
–Intervention or programme effectiveness
–For improving underlying conditions

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6
Q

What is evaluation epidemiology

A

Measures the effectiveness of different health services and programmes
•Answer question
–So what?
–Have there been any improvement in health status?

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7
Q

Epidemiology aims about Information needed for:
– Planning
–Managing
–Evaluating
•All the activities required to promote health and to prevent and control disease
True or false

A

True

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8
Q

What is the denominator population

A

Population at risk (denominator population)
–People at risk of developing a disease or having a health problem
–People currently suffering from it

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9
Q

The concept of denominator help develop the information needed for:
–Health planning
–Management of health programmes
–Evaluation of health promotion and disease control activities true or false

A

True

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10
Q

Example of who variables,where variables and when examples in descriptive epidemiology

A 
Age
–Sex
–Education
–Occupation
–Income
–Cultural and religious group
–Family size
–Nutritional state
–Immune status
•Other characteristics
–Hospital attendance
–Birth weight
–Sanitation in households
Where?
•Variables
–Town, village or isolated dwelling
–High or low altitude
–Proximity to river, forest, wild animals or sources of toxic substances
–Distance from health services

When?

New cases of Avian Infuenza per day
•New cases of malaria per week
•New pregnant mothers registering per month
•New cases of HIV in one year

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11
Q

Wht Is the best indicator for assessing the condition of event/case/episode

A

Incidence

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12
Q

What It is the best measure for evaluating health programme effectiveness
–Used in disease surveillance and for analyzing the use of health services

A

Incidence

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13
Q

What is used to measure frequency

A

Incidence and prevalence

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14
Q

Incidence is used for Useful for diseases with short average duration
True or false

A

True

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15
Q

Prevalence is Total number of existing cases/episodes/events occurring at one point in time commonly on a particular day
–Prevalence = Incidence x average duration of the condition
–Useful for chronic conditions
True or false

A

True

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16
Q

What kind of surveillance provides prevalence information

A

Cross sectional survey

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17
Q

Numbers are the most readily available data
•Often used in monitoring the occurrence of important infectious disease, esp.
–in outbreaks
–When
•populations are restricted in time and locality and
•population structure is assumed to be stable
True or false

A

True

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18
Q

•Rates are calculated by relating the cases to the population that which has given rise to them.
•Number of cases (numerator)
–Made up by counting people, episodes or attendances.
•Total population at risk (denominator)
•Rates must have time period or a date attached to it which must always be stated
True or false

A

True

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19
Q

Stage two uses of rates

A

To make comparisons

•To calculate the number of expected cases

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20
Q

What are the formulas for incidence and prevalence rates

A

Incidence rate= new cases in specified period of time x factor
total population at risk
•Prevalence rate= existing cases at specified point of time x factor
total population at risk

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21
Q

In estimating the prevalence rate of a particular disease, the denominator used should be;
– the total number of individuals who may be at risk of contracting the disease in question true or false

A

True

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22
Q

In case of survey, denominator may comprise of all individuals in the sample.
•For age-sex specific rates, the denominator includes only the people in relevant age-sex groups.

True or false

A

True

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23
Q

In estimating effectiveness of a programme we need total number of new episodes (incidence) commonly in one year
•In studying use of health services, we look at information on new and repeated attendance

True or false

A

True

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24
Q

How are cases classified

A

Possible
•Cases which have symptoms of possible disease (fever, headache, body aches)
–Probable
•Possible cases who also respond to treatment
–Definite
•Probable cases who test positive to diagnostic test

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25
Q

What are health indicators and importance of health indicators

A

Indicators are measures used to describe an existing situation and to measure changes or trends over a period of time

To analyse present situation
•Make comparisons
•Measure changes over time
•Provide measures for development

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26
Q

Health indicators may measure the actual situation directly
–IMR direct measure of actual risk of infants dying in their first year of life
–Indirectly as a measure of overall socioeconomic development
True or false

A

True

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27
Q

Name five sources of information for calculating health indicators

A 
Registration of births, death ad diseases
•Population censuses
•Routine health information systems
•Surveillance
•Investigation of epidemics
•Sample surveys
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28
Q

What’s re the types of health indicators

A

Health policy
–Level of political commitment to PHC
–Availability of public policy statements and health plans
–Degree of equity in the distribution of resources
•Social and economic development
–Level and distribution of economic wealth
–Types and levels of employment
–School enrolment and adult literacy
–Household food security
•Population
–Age-sex structure
–Density, distribution and migration
–Population growth: birth and death rate, fertility and rate of natural increase
•Provision of health care
–Access to health care and facilities and coverage by the 8 essential elements of PHC
–Resource availability
•Health status
–Nutritional, morbidity and mortality

Health policy indicators
Social and economic development indicators
Population indicators 
Provision of health care indicators 
Health status indicators
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29
Q

Morbidity indicators are based on? And name three mortality indicators (morbidity and mortality indicators are health status indicators)

A 
Based on disease specific incidence or prevalence rate for common and severe diseases
•Mortality indicators
–Crude mortality rate
–Infant mortality rate
–Under five mortality
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30
Q

Infant under 1year make up 3-4% of total population
–Children under five (about 18-20%)
–Children 0-14 years (about 40-44%)
–Women in fertile age range (15-44 years) 20-22%
–Women and young children 40%

What kind of country does this population census represent and what is the importance of population census

A

Developing county and it These rates help estimate absolute number per population group

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31
Q

Age-sex structure can be show by population pyramid using the percentage of males and females in each 5 year age group
•Population pyramids provides an estimate of denominators (at risk population) for calculating
–Age and sex specific rates
True or false

A

True

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32
Q

What is population density and its importance

A

The average number of persons per square kilometre (km2)
•Density may vary from place to place
•Useful for planning health services and in evaluating the access to and coverage of different health programmes

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33
Q

Crude birth rate is estimated from?

A

Estimated from census or

–special demographic survey

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34
Q

What is the formula for crude birth rate and total birth and what is the crude birth rate for high fertility countries and low fertility countries

A

CBR= Total births in one year/total midyear population (all ages, same year) x 1000
–High fertility countries – 45births per 1000 per year
–Low fertility countries- 20births per 1000per year
–Could be use in estimating the total number of births per year
•Total birth = CBR/1000x population per year

35
Q 
Fertility rate (FR) is an age-sex specific rate usually derived from census or special demographic survey
•It’s a measure of how frequent women in the fertile age range are having babies
What is the fertility rate of women in developing countries
A

Developing countries have between 100-150 births per 1000 women aged 15-44 years

36
Q

What is the formula for crude death rate, infant mortality rate and child mortality rate and maternal mortality rate and what is the infant mortality rate in developing countries

A

Crude death rate
– total death in one year/total midyear population (all ages, same year)x 1000
•Infant mortality rate
– the proportion of all liveborn infants who die in the first twelve months of life
– total infant (aged < 1 year) deaths during one year/total births in the same year x1000
–
In developing countries rates range between 60-150 infant deaths per 1000 births per year in severe conditions 200
•Neonatal mortality is infant deaths in the first 1month of life

Demographic rates
•Child mortality rate: based on deaths between 1-4 years

Maternal mortality rate
–Maternal pregnancy related deaths in one year/ total births in same year x factor (1000 or 100000)

37
Q

What is population growth and the formula for rate of natural increase or RNI

A

Population growth
–Balance between the number be of births and people migrating into the an area on one hand and the number of deaths and people migrating out the area on another hand
•Rate of natural increase
- RNI=CBR-CDR

38
Q

Name two sources of population information

A

Census report

•Studies report

39
Q

Accuracy of population data is limited by

A

Resources available for their collection
–The level of socioeconomic development
–Educational and cultural sophistication of the population itself

40
Q

Age is one of the most difficult variable to ascertain accuracy.
•It is closely related to disease patterns
•People may not know their age but may know the year they were born
•Asking both questions can help validate age
•Age can also be estimated according to a calendar of notable events
–Eg how many years after independence were you born as a way of improving accuracy of population characteristics
True or false

A

True

41
Q

Sex is important to record because of the physiological and behaviour patterns in the two sexes
•The sex composition of a survey population and a general population can invalidate result
•The under enumeration of women is high in most surveys

True or false

A

True

42
Q

Ethnic group share similar social and cultural characteristics which does influence disease patterns
–thus, differences in disease frequencies among ethnic groups

True or false

A

True

43
Q

Marital status
•A precise definition of married and separated may be problematic in some societies
•These are mainly due to the social roles attached to the status.
True or false

A

True

44
Q

Occupation
•There is the need to decide whether the past or present occupation is needed.
•This would be important in identifying risk respondent could be exposed to.

True or false

A

True

45
Q

Name five demographic variables

A 
Marital status 
Occupation
Ethnic group
Sex
Age
Religion
Place of residence
46
Q

The most available source of morbidity data is hospital records
True or false

A

True

47
Q

What are the two ways important diseases may be under recognized by district information system

A

If disease has low frequency (incidence or prevalence)
–When illness does not produce clear symptoms and signs that are easily recognized by the people or health workers eg malnutrition
•These require special surveys and research studies for subclinical and chronic infections
•Same applies to mental disability and eye diseases

48
Q

Reliable disease specific incidence or prevalence rates could be used to calculate approximate number of cases
Therefore what is the formula for number of cases

A

No of Cases = prevalence rate x total population
–Useful for chronic diseases
–Could be affected by seasonal or annual fluctuation
–Useful in assessing the effectiveness of health services
–Exposes the limitations in relying on incidence and prevalence rates calculated from cases reported by routine information systems

49
Q

A small increase in the total number of cases or deaths may signify that an undetected epidemic is already under way in the community
What is the formula for case fatality rate

A

Case fatality rate= number of patients dying from a disease/number of cases of the disease, diagnosed in same period x 100
–Useful in assessing the quality of treatment given by medical services
–Case fatality of 15% is high
–Must be interpreted taking into accounts the severity of illness
–Case fatality in epidemics can give clear indication of the severity of illness and could help identify disease causing the epidemic

50
Q

Death certification records the cause of a person’s death, as stated by a doctor or another responsible health worker.
death registration can be useful in compiling mortality statistics and in the surveillance of specific diseases.
•Could be useful in evaluating disease control activities and a rise in certified deaths from
–a particular cause may indicate a serious outbreak
–Mortality data has the advantage of been more accurate than morbidity data
–Disadvantage is that only fatal cases are included
–Data might be deficient when not certified by a doctor
–Under- registration of deaths
Medical Certification compiling statistics, deaths are classified by underlying causes and not the direct cause.
True or false

A

True

51
Q

The collection and reporting of health information data is country specific
What is its purpose

A

The purpose of data collection is to support:

– Management and evaluation of health activities

52
Q

How do health information systems work

A

Health facilities,communities detect new cases,collect the info about it,analyze the info and send the info to the regional level and it send a it to the ministry of health where info is reported and disseminated
Then they also improve health planning and implement necessary changes in those health facilities and communities

53
Q

For a system to be useful, it does not have to detect all cases
•Good estimates of incidence can be invaluable for planning and evaluation of health programmes
True or false

A

True

54
Q

Trends over time can be forecast when proportion of cases detected remains constant over time
•Incomplete data are better than none, provided the problems and defects in the data are
True or false

A

True

55
Q

What’s re the two ways surveillance is used

A

The continuous scrutiny of the factors that determine the occurrence and distribution of disease and other conditions of ill health.

i. It is essential for effective control and prevention
ii. Includes the collection, analysis, interpretation and distribution of relevant data
iii. Similar to health information system
2. A special system which is set up for particularly important health or disease eg
i. Spread of communicable disease in a disaster
ii. Nutritional status in a famine or an epidemic

56
Q

What is the aim of surveillance

A

To provide quickly information which can be analysed to determine frequency (Usually incidence), and to answer questions: who? Where? And when?

57
Q

Name five uses of epidemiological surveillance

A

To identify outbreaks and epidemics to ensure effective actions
•To monitor the implementation and effectiveness of control programmes
•To assist in the planning of health programmes
•To identify high risk groups, geographical areas and variations over time
•To increase knowledge on causative agents and dynamics of transmission of communicable disease

58
Q

Name three diseases under international health regulation, five diseases under global surveillance and four diseases under research

A

International health regulation (Download and read)
–3 diseases namely cholera, plague and yellow fever)
•Global surveillance
–5 diseases (typhus, influenza, malaria, poliomyelities and relapse fever) currently we have NCDs and childhood obesity
•UNDP/WB/WHO Special programmes for research
–Filariasis, leishmaniasis, leprosy, malaria,

59
Q

What is the possible diagnosis for these symptoms Fever with red rash, red eyes, disappearing within a week

A

Malaria

60
Q

What is the symptom of poliomyelitis

A

Fever with paralysis

61
Q

Symptoms of cholera are

A

Sudden and severe watery diarrhoea with massive and rapid dehydration

62
Q

Symptoms of African trypanosomiasis

A

Fever, swollen glands in back of neck, lassitude, headache, sleepiness

63
Q

What is the possible diagnosis for this disease Segments expelled in faeces

A

Tapeworm disease

64
Q

Fever, rigors, headache, body aches, inability to carry out normal daily activities
What causes these symptoms

A

Malaria

65
Q

Name five sources of information in health information systems

A

Health facilities
–Main source of information
–Information sent in forms of reports

Death registration
–Useful in areas where a high proportion of deaths are registered
–Can be useful in epidemics when a few deaths are dispersed over a wide area
•
Laboratories
–Useful for information based on special test that isolate an infectious organism or confirm diagnosis
–Challenge in the distribution of laboratories

Community surveillance of limited number of key diseases and problems
–Useful to staff employed in special programmes such as malaria and family planning
–Uses simple standardized diagnostic criteria

Special searches
–Schools, markets, particular villages, and high risk households for case dections
•

Investigation of outbreaks
–Outbreaks require active case finding by surveys and details recorded and notified
•

Surveys
–Useful for periodic surveillance of some conditions
–Useful in estimating coverage of regular reporting or surveillance systems and

66
Q

What’s re the deficiencies of health facilities as a source of information

A

Use of health facilities is influenced by
•Distant from homes
•Cost of treatment
•Uneven distribution of facilities among communities
•Local attitude to disease or conditions

67
Q

Reporting on cases are done by analysing registered data on basis of
–Who (age and sex)
–Where (village of onset
•Ideally cases should be reported by date of onset but it is practically impossible so date of diagnosis is usually reported
•Trend analysis could also be performed

True or false

A

True

68
Q

Information from a reporting or surveillance systems must be communicated with relevant stakeholders
–Ministry of health
–Primary health care workers and district staff
–Village councils and organisations
–Nongovernmental and voluntary organisations
–Local mass media, radio
•The usefulness in improving planning of health programmes and disease control activities.

True or fake

A

True

69
Q

Most important epidemics are due to communicable diseases with short incubation period that are easily transmitted.
–E.g. food borne diseases and cholera
•The epidemicity is relative to the previous incidence of the disease in the same area, among specific population groups and at different seasons of the year.

True or false

A

True

70
Q

Name three causes of epidemics

A

Food borne outbreaks
–E.g. enteritis due to Escherichia coli, staphylococcal infection, salmonellosis
•Communicable disease with short incubation period
–E.g. Dengue, cholera, influenza, malaria, measles, plague, yellow fever
•Toxic substances
–E.g. contaminated foods, insecticides and agricultural chemicals

71
Q

How to detect epidemics

A

Community leaders, such as Assembly men and teachers
•Health workers in primary health care facilities
•District health information and surveillance system
•Hospitals
•Epidemics could highly be a political issues and reporting must be done with absolute caution

72
Q

How to describe epidemics

A

Information on age, sex, residence and occupation of known cases in needed
•Date and time of onset and the whereabout of cases during incubation of disease
•Basic questions to consider
–What is the disease causing the outbreak?
–What is the source?
–What is the mode of transmission?
–How an the epidemic be explained?
•Who, when and where analysis required

73
Q

What is epidemic incidence curb

A 
Epidemic incidence curve
•Is a graph that plot cases of the disease by  time of onset of the illness.
•The graph can indicate
– the nature of the outbreak
–Probable source
74
Q

Difference between point source and extended point source

A

Point source or common source
–Where there has been simultaneous exposure of many susceptible to a pathogenic agent resulting in a rise in the incidence of cases of the disease over a short time.
–Characteristics of water borne and food borne diseases
•

Extended point source
–where the point source provides continuous exposure over a longer period of time
Common to shigellosis

75
Q

The shape of a propagated epidecim curve depends on

A

incubation period of the disease and

–Suitability of the environment for transmission

76
Q

The longer the incubation period, the more spread out the cases will be.
•Contact spread outbreak,
–the crowding and intimacy of contact will determine the rapidity epidemic reaches a peak
–While the proportion of susceptible population will influence the extent of the outbreak

True or false

A

True

77
Q

Analysis of cases by who personal factors such as age, sex and occupation may also give clue to source of the infection
•It may be important to calculate attack rate in different population groups

The clustering of cases together in one area about the same time indicates a localized epidemic true or false

A

True

78
Q

How is case control analysis done

A

Descriptive analysis by who, where? And when?
–may provide sufficient information about the source of the outbreak for immediate appropriate control action
•Case control study is often used
–Patients are questioned to assess their possible contact with the source as suggested by the incubation period
–Similarly controls from the same area who do not have the disease are posed the same questions

79
Q

Importance of attack rates

A

Useful in food borne epidemic
•Comparing the attack rate for illness among the exposed to the unexposed
–(those who ate a particular food to those who did not)

80
Q

Elements in the control of epidemics

A

Attack source and mode of transmission
•Treat and isolate all cases
•Increase resistance of local population
•Continue surveillance

81
Q

What are the main strategies for control of. A communicable disease epidemic

A 
Attack the source:
Treat the case and carriers
Isolate cases
Surveillance of suspects
Control of animal reservoirs
Notification of cases
Interrupt transmission :
Environmental hygiene 
Personal hygiene 
Vector control
Disinfection and sterilization 
Restrict population movements 
Protect susceptible people:
Immunization 
Chemoprophylaxis
Personal protection 
Better nutrition
82
Q

a relative risk of 1.5 means that the risk of the outcome of interest is 50% higher in the exposed group than in the unexposed group, while a relative risk of 3.0 means that the risk in the exposed group is three times as high as in the unexposed group
True or false

A

True

83
Q

For example, if the absolute risk of a condition is 30% in the reference population, then an RR of 1.2 means that this risk will increase by 20% after exposure to the risk factor. As 20% of 30 is 6%, the absolute risk will rise from 30% to 36% in patients exposed to the risk factor.
True or false

A

True

Epidemiology (7 decks)

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