Medical Council of India

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(outsourced or otherwise) to cater to the referral transport of sick neonates and children. ...... been undertaken in parts of. Surinam, Malaysia and South Africa.








The Reproductive and Child Health Program is the flagship program of the Department of Family Welfare in the Ministry of







Concentrates on intensive development of human resources through strengthening of program and institutions and enhancement of skills, complemented by an efficient support system to enhance the quality of M&E, procurement, financial management and service delivery. However, it has implementation constraints of Weak management capacity especially in planning, M&E, supervision, budgeting, implementation of civil works, IEC and in the delivery of quality services. Recently held RCH II consultation reiterated the emphasis on the NHP 2002 & on the epidemiological and Public Health Management training of the District level managers of Public Health activities.

The existing educational programme in medical colleges promotes the knowledge of epidemiology but it has not been able to inculcate the epidemiological skills in undergraduates, which are important for programme planning, monitoring & evaluation. In order to prepare future health managers it is imperative that they possess good understanding of practice of epidemiological principles in programme management. In


case the medical graduates develop skill in application of epidemiology than it will help them, not only for understanding of disease dynamics for its effective control but also for need based health planning, effective monitoring & efficient supervision of health programmes including RCH. It will also help in developing the concept of an efficient management information system.

In NHP 2002, the public health management training of health managers has been recommended. The weakness of programme management at present includes lack of epidemiological skill for community diagnosis as well as for planning & evaluation. The proposed module will go a long way to overcome this shortcoming. The module will also fulfil the requirement of the Medical Council of India, which recommends that: The undergraduate students coming out of a medical institute should: (a)Be competent to practice preventive, promotive, curative and rehabilitative medicine in respect to the commonly encountered health problems; (b)

Possess the attitude for continued self-

learning and to seek further expertise or to pursue research in any chosen area of medicine.


(c)Be familiar with the basic factors, which are essential for the implementation of the National Health Programmes including practical aspects. (d)

acquire basic management skills in the area

of human resources, materials and resource management related to health care delivery; (e)be able to identify community health problems and learn to work to resolve these by designing, instituting





outcome of such measures; It will be difficult for an undergraduate to practice the above without possessing the appropriate epidemiological skills.

Learning Objectives: The following learning objectives were kept in mind at the time of conceiving & development of the module:  The intern should be able to understand the relevance & importance of epidemiological skills in discharging the duties as basic medical doctor in PHC& other settings  The intern should able to practice the epidemiological skills in PHC setting  The intern should be able to understand & apply the epidemiological principles in management of various National Health Programmes.


 The intern should be able to understand the importance of epidemiology in pursuing the research.

Advice to Facilitators: The facilitators are advised to promote the module teaching in small groups & should adopt the modules in local settings depend upon the available resources. At the same time, the facilitator should be able to create enthusiasm & interest through educational games & examples based on his experience. The facilitator has a responsibility to promote group discussion & critical thinking among interns for better undertaking of the module.

Instructions to Interns to acquire learning skills As an adult learner, the intern should: 

Assume responsibility for learning.

Lead and

participate in the discussion. The interns will not be given lectures. The interns should strive to be selfdirected; that is, to find out information on your own using varied learning resources. 

Develop a rich reservoir of knowledge, skill, beliefs, and concepts that can serve as learning resources. The module will allow you to activate or explore your prior knowledge and process new information.


Seek to learn in the context in which the information will be used.

The module will enhance contextual

learning. 

Expect your teacher to act as a facilitator and mentor, rather than a source of solutions.

Anticipate that the problem will not to be solved in one session.

Be given time to search for and find your own solution(s) to the problem, and report back to your facilitator.

Enjoy learning in a non-threatening environment, created by a facilitator.

All the exercises provided in the module should be undertaken in the same sequence for better learning.

The interns may require pocket calculator & lead pencil in solving the exercise & to do the rough work.

Few blank sheets are attached in the end of chapter for doing calculations & making your notes.

References: Medical Council of India- regulations on Graduate Medical Education, 1997- MCI, New Delhi Anthony R. Measham, Richard A. Heaver, “India’s Family Welfare Program” – Moving to a Reproductive and Child Health Approach; The World Bank, Washington, D.C.


Tentative Programme DAY – 1 - Pretest & Overview

60 minutes

- Epidemiology Module

90 Minutes

Measurement of frequencies, Morbidity & Mortality - Discussion

30 Minutes

DAY – 2 - Recap & Feedback

30 Minutes

- Measurement of Disability & fertility

45 Minutes

- Application of frequencies

45 Minutes

DAY – 3 (a) Feedback & Recap

30 Minutes

(b) Epidemic Investigation

45 Minutes

Day 4Epidemiological Exercises

45 Minutes

DAY – 5 (a) Feedback & Recap

30 Minutes

(b) Introduction on Management Science

30 Minutes

(c) System Framework & its application including exercise

60 Minutes

(d) Practical Application of Management sciences including 60 Minutes supervision & Financial Management exercises. DAY - 6 (I) Recap & Feedback

30 Minutes

(II) Material Management & its exercise

45 Minutes

(III) MIS & its exercise

75 Minutes

(IV) Communication

30 Minutes

DAY - 7 (I) Recap & Feedback

30 Minutes


(II) Introduction to Research Methodology

30 Minutes

(III) Steps in Research

60 Minutes

(IV) Sharing a research Protocol of the department & give a 60 Minutes small exercise on a topic of Interns interest (Homework) DAY - 8 (I) Recap

30 Minutes

(II) Discussion of Research Methodology

60 Minutes

(III) Introduction to RCH

30 Minutes

(IV) Package & service under RCH programme including 60 Minutes exercise DAY - 9 (I) Recap

30 Minutes

(II) Newer Initiatives in RCH

60 Minutes


60 Minutes

(IV) Instruction to field exercise on CNA / PRA

30 Minutes

DAY - 10 Field exercise on Spot Map & FGD DAY- 11 (I) Recap

30 Minutes

(II) Presentation of Field Exercise

90 Minutes

(III) Sub Centre & PHC Plan

60 Minutes

DAY - 12 (I) Recap

30 Minutes


30 Minutes

(III) Quality Assessment including exercise

120 Minutes

DAY - 13 (I) Recap

30 Minutes

(II) Communication & Counseling with exercise (To be 90 Minutes


developed at local level) (III) Surveillance

60 Minutes

DAY – 14 Post Test


ESSENTIALS OF EPIDEMIOLOGY Learning Objectives: At the end of chapter the intern should be able to: 1. Understand basics of epidemiology 2. Know the various sources of data and their importance 3. Calculate various frequencies in relation to health and related events in different health care settings 4. Analyze, interpret and apply the data for planning, monitoring and evaluation of health program 5. Understand and use different ways of presentation of data 6. Learn the process of investigation of epidemic

Let us revise the basics of epidemiology, relevant to planning, implementation, monitoring & evaluation of RCH & other national health programme Knowledge and skills of epidemiology are essential for the health professionals to understand health problems of the community and application of that for the prevention and control of diseases. It will help them to study trend (rise and fall) of disease in the population, understand causes and risk factors of the health related events, to prioritize, plan, monitor and evaluate various health care services.

Theoretical learning of essentials of epidemiology has been a part of your undergraduate curriculum. You will require more exposure that is practical throughout your careers. Internship period is the most suitable to acquire the practical training through self-learning module particularly during their posting in community medicine department. The skill so develop will go a long way in developing proper understanding towards health care to the people and would help in achieving goal of health for all. Without such training, you are likely


to be prejudiced and inclining towards curative approach to the health problems. The training will help you to understand the problems in the right perspective by taking population as denominator, such for etiological factors and practice the concept of comprehensive health care. This will inculcate the culture of evidence based health care approach. In the developing countries, resources are scarce and such training will help you in finding out cost effective strategies as solutions to the problems. Definition of Epidemiology: Epidemiology has been defined as “study of the distribution & determinants of health related states or events in a specified population, and the application of this study to control of health problems” (Last 1988). “Study” includes surveillance, observations, hypothesis testing, analytic research & experiments. “Distribution” refers to analysis by time, place & classes of persons affected. “Determinants” are all physical, biological, social, cultural and behavioural factors that influence health.

Types and Sources of Data: Various types and sources of data are as follows: i. Primary data:

The data collected by an investigator in the

field, through cross sectional or longitudinal survey, (In case you do not remember the cross sectional or longitudinal survey, please discuss with your facilitator.) ii Secondary data:

When data obtained from published or

unpublished sources e.g. Medical Record Department, Private Practitioners, and Survey Reports namely National Family Health


Survey, Reproductive & Child Health report, textbooks, journals, annual and other reports published by various health agencies.

Exercise: Visit a DOTS Center / Sub center / Primary Health center and procure secondary data and comment on it. Space for Exercise:



Data collected from any of the above sources is expressed in terms of variables. Variables are those characteristics or attributes that vary from person to person, from time to time, and from place to place. Thus single measurement of height is not a variable but height of persons is a variable.

These variables are measured using suitable scales. The variables may be qualitative & Quantitative. The Qualitative variables are of four categories of measurement scales: (1) Nominal scales, in which observations are classified into categories (e.g. classification of disease, gender); (2) Ordinal scales, which assign rank orders to categories (e.g., mild, moderate, and severe); (3) Interval scales, in which the distance between two measurements are defined (e.g. temperature, scores on intelligence tests); and (4) Ratio scales in which both the distance and ratio between two measurements are defined (e.g. length, incidence of disease, number of children). In both ratio and interval scales, it is possible to specify the extent to which one measurement is larger than another (e.g. 70 oC is 35 degrees warmer than 35oC, one meter is 50 cm longer than 50 cm).

However, a ratio scale has the additional possibility of

specifying the ratio between two measurements (e.g., one meter is twice as long as 50 cm).


The Quantitative variables are of two types:

1. The variables are called continuous if they can be continuously refined to measure more accurately. For example, no matter how accurately length is measured; it is always possible to make a more accurate measurement by further subdividing the measurement instrument.

2. The variables are called discrete if such refinements are not always possible. For example, it is not possible to refine continuously the measurement of the number of children because there are no possible values between zero and 1, 1 and 2, and so on.

The data collected on variables needs to be converted into useful information using various appropriate measures of frequency. Measurements of Frequencies: In epidemiology measurement of frequency regarding distribution and determinants of health and health related events is essential. Various parameters are used for calculations of these frequencies. Let us learn the important parameters used in epidemiology: Rate, Ratio, and Proportions: Rate:

The rate is the occurrence of a particular event in a population during a given time period. Example: Crude Death Rate


No. of deaths in one year Death rate= _____________________ X 1000 Mid- year population

e.g., 24 deaths occurred in a village having mid-year population of 4000 Calculation: Death rate in that village = 24X1000/4000=6 per 1000 population Note:

Rate comprises the following elements- numerator,

denominator, time specification and multiplier. The time dimension is usually a calendar year. The rate is expressed per 1000 or some other round figure selected according to the convenience or convention, to avoid fractions. Types a. Crude Rates: birth and death rates. These are unstandardized rates. b. Specific rates: disease specific, age and sex specific, time specific. c. Standardized rates: these are obtained by direct or indirect method of standardization or adjustment e.g. age and sex standardized rates.


It expresses a relation in size between two random quantities. The numerator is not a component of denominator. The numerator and denominator may involve an interval of time or may be instantaneous in time. Broadly, ratio is the result of dividing one quantity by


another. It is expressed in the form of x: y, e.g. sex ratio, doctorpopulation ratio, child-woman ratio, etc. Say sex ratio is 933: 1000.


is a ratio, which indicates the relation in magnitude, of a part to the whole. The numerator is always included in the denominator. It is usually expressed in percentage, e.g. percent of under five children suffering from malnutrition of the total under five populations. Say a proportion of 60% of the under five children is suffering from malnutrition.

Concept of Numerator and Denominator:

For calculation of rate, ratio or proportion proper understanding of the Concept of Numerator and Denominator is very important. a. Numerator: Numerator refers to the number of times an event (e.g. number of birth) has occurred in a population, during a specified time period.

b. Denominator: Numerator has little meaning unless it is related to the denominator. The epidemiologist has to choose an appropriate denominator while calculating a rate. It may be related to: (I) population (II) the total events.

(I) Denominator related to the population: (i)

Mid year population: Because the population size changes daily due to births, deaths and migration, the mid year


population is commonly chosen as a denominator. The population as on 1st July is mid-year population.


Population at risk: It is important to note that the calculation of measures of disease frequency depends on correct estimates of the numbers of people under consideration. Ideally, these figures should include only those people who are potentially susceptible to the disease studied. For instance, men should not be included in denominator for the carcinoma of cervix.

Part of population, which is susceptible to a disease is called the population at risk, e.g., Occupational injuries occur only among working people so the population at risk is the workforce.


Person – time: In some epidemiological studies (e.g. cohort studies), person may enter into the study at different times. Consequently, they are under observation for varying time period. In such case, the denominator is a combination of person and time. The most frequently used person time is person- years. Some times this may be person months, person weeks or man- hours. For example, if 10 persons were observed in the study for 10 years, person time would be 100 person years of observation. The same figure would be derived if 100 persons were under observation for one year.







summarizing the experience of persons with different duration of observation or exposure. 23


Sub groups of the population: the denominator may be subgroups of population e.g. under-five, female, doctors, etc.


Denominator related to total events: In some instances, the denominator may be related to total events instead of the total population, as in the case of infant mortality rate the denominator is total number of live births.

For better understanding of epidemiology, you should understand the following statistical concepts: Normal Distribution: Large number of observations when distributed according to their values shows certain patterns. Let us suppose, we collect the hemoglobin values of a very large number of people and make a frequency distribution with narrow class interval we are likely to get a smooth symmetrical curve.

Such a curve is called normal

distribution. The normal distribution or normal curve is an important component in statistical theory. The shape of the curve will depend on the mean and standard deviations, which in turn will depend upon the number and nature of the observations.

It is useful to know at this stage that in a normal curve (figure): (a) the area between one standard deviation on either side of the mean (mean + 1 S.D.) will include approximately 68% of the values in distribution, (b) the area between two standard deviation on either side of the mean (mean + 2 S.D) will cover approximately 95% of the values, and (c) the area between (mean + 3 S.D) will include 99.7% of


the values. These limits on either side of the mean are called confidence limits and are shown in the figure.

The probability of an observation falling outside + 2SD is 1 in 20. Hence the observation fall beyond this limit it is considered to be statistically significant. Normal Distribution Curve

Measures of Central Tendency:

We need to workout averages for large number of values to make some sense. It gives the mental picture of the central value. There are several kinds of average, of which the commonly used are arithmetic mean, mode and median. Averages are measures of central value, therefore they locate the center or mid point of a distributions.

(a) Mean: To obtain the mean the individual observations are added together, and then divided by the number of observations.

(b) Mode: The mode is the most commonly occurring value in a distribution of data. 25

(c) Median: To obtain the median, the data is first arranged in a descending and ascending order the value of middle observation is located, which is called median. Exercise: Calculate mean, mode, and median for hemoglobin values of 20 pregnant women. 12, 10, 8, 9, 12, 10, 7, 9, 7, 10, 11, 8, 12, 7, 8, 13, 11, 9, 10, 11, 7



Mode: Measures of Dispersion:

(a) Percentile: Sometime one has to locate other points in the range. This can be done with the help of percentile. Just as the median divides the subjects in two equal groups each with nearly n/2 subjects, the percentiles divide the subjects in 100 equal parts. Each part is containing n/100 subjects. If n= 400, each part will have 4 subjects. The parts are identified by 99 cut points of the measurements under consideration. Consider weight to nearest Kg. of 2 yr old 35 boys:

10, 12, 9, 11, 10, 12, 12, 13, 8, 9 13, 14, 13, 8, 9, 11, 11, 10, 12, 13, 9, 12, 10, 11, 14, 9, 12, 12, 13, 12, 9 13, 10, 11, 10,


For example 20ths percentile of weight is that value below which are 20% children, for n=35, then 20% of children mean 7 children. The procedure is to arrange their weights in ascending order and pick up the seventh value. When arranged in ascending order, there weights in Kg. are:

8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 13, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 14, 14 The seventh value is 9 kg. This is the 20th percentile of weight of 2 yr old boys as far as these data are concerned. Similarly we can find out given percentile by adopting the above procedure. It can be determined by the formula [kth percentile = (k X n/100)].

(b) Deciles, Quartiles and Tertiles:

Deciles divide the group of subject in to 10 equal parts. Quartiles in to four equal parts and tertiles into three equal parts. Tertiles are often used to divide the subjects into those with low, medium and high values.

Measurements of Morbidity: Morbidity data should be accurately and completely collected and transformed into various rates to make the understanding of magnitude of the health related event meaningful.


Incidence Rate (IR):

It is the number of new events that occurs in a defined time period in a geographical area. The denominator is the population at risk for that event during that period. The most accurate way of calculating incidence rate is person-time incidence rate. Each person in the study population contributes one-person year to the denominator for each year of observations before disease develops or the person is lost to follow-up.

No. of people who get a disease in a specified period IR =______________________________________________X 1000 Sum of the length of time during which each person in the population is at risk.

The incidence rate takes into account the variable time periods during which individuals are disease free and thus at risk of developing the disease. Since it may not be possible to measure disease free periods precisely, the denominator is often calculated approximately by multiplying the average size of the study population by the length of the study period. This is reasonably accurate if the size of the population is stable and I.R. is low. For example, in a sub-center with population of 5000 there are 5 new cases of tuberculosis occurred during one year. For this disease the whole population is at risk of tuberculosis, hence the incidence rate of tuberculosis would be 1 per 1000.

Similarly, incidence rate can be calculated for health related event, such as failure rate per hundred woman years of exposure (HWY). 28

This rate is also known as “Pearl index”. It is normally used for studying the effectiveness of a contraceptive. pregnancies


The number of

all pregnancies, whether these were

terminated as live birth, still births or abortions or had not yet terminated.

Failure rate per HWY = Total accidental Pregnancies/Total months of exposure X 1200

In applying the above formula, the total accidental pregnancies shown in the numerator must include every known conception, whatever is the outcome. The multiplier 1200 is the number of months in 100 years. The total months of exposure is the denominator obtained by deducting 10 months for a full pregnancy and 4 months for an abortion.

A failure rate of 10 per HWY would mean that in the lifetime of the average woman one fourth or 2.5 accidental pregnancies would result since the average fertile period of a woman is about 25 years.

In designing and interpreting a contraceptive use effectiveness trial, a minimum of 600 months of exposure is usually considered necessary for drawing valid conclusion.

Special Incidence Rates:

(a) Attack rate: The attack rate is defined as number of new cases of a specified disease during a specified time interval per 100 29

populations at risk during the same time interval. An attack rate is used only when the population is exposed to risk for a limited period of time such as during an epidemic. Formula:

Number of new cases of a specified disease during a specified time interval Attack rate = ------------------------------------------------------------ X100 Total population at risk during the same time interval

(b) Secondary attack rate (SAR): is defined as the number of exposed persons developing the disease within the range of incubation period following exposure to a primary case. Formula:

Number of exposed persons developing the disease within the range of incubation period SAR = ------------------------------------------------------------------X 100 Total number of exposed/ susceptible contacts

The denominator consists of all persons who are exposed to case. More specifically, the denominator may be restricted only to susceptible contacts. The primary case is excluded from both numerator and denominator.

Example: Suppose there is a family of 6 consisting of 2 parents (already immune) and 4 children who are susceptible to a specific disease, say measles. There is a primary case and within a short time 2


secondary cases among the remaining children. The secondary attack rate is 2/3 or 66.6%.

2.2. Prevalence: The total number of all individuals who have an attribute or disease at a particular time or during a particular period divided by the populations at risk of having the attribute or disease at this point of time or midway through the period. Although referred as rate, prevalence is really a ratio.

2.2.1 Types a) Point Prevalence: The data have been collected for one point of time. The point in, point prevalence may for all practical purposes consist of a day, several days or even a few weeks depending upon the time taken to examine the population sample. b) Period Prevalence: It measures the frequency of all current cases (Old & New) existing during a defined period of time (e.g. annual prevalence) expressed in relation to a defined population. It includes cases arising before but extending into or through the year as well as those cases arising during the year.

No. of existing cases (old & new) of a specified disease during a given year (period of time interval) Prevalence=-------------------------------------------------------------X1000 Estimated mid year (interval) population at risk


Factors influencing Prevalence Increased by:  Longer duration of illness.  Prolongation of life of patients without cure.  Increase in new cases  Immigration of cases  Emigration of healthy people  Immigration of susceptible people  Improved diagnostic facilities  Better reporting

Decreased by:  Shorter duration of disease.  High case fatality rate from disease  Decrease in new cases  Immigration of healthy people  Emigration of cases  Improved cure rate of cases

2.2.2. Relationship of Incidence with Prevalence Prevalence depends upon two factors- the incidence and duration of illness P=IXD = Incidence X mean Duration Example: If incidence is 10 cases / 1000 people per year and mean duration of disease is 5 years, then Prevalence = 10 X 5 = 50 / 1000 population.


Similarly we can derive incidence and duration if other variables are known as follows: I = P/D , D = P/I Exercise: In a population of 1000, following are the details of cases of tuberculosis. Calculate incidence, point prevalence (as on 1st July) and period prevalence for 2001 and comment on it. Case No

Detected on

Died / Cured on


Jan 12, 1999

March 13, 2001


Feb 13, 1999

Dec 18, 2000


April 29, 1999

Not cured upto 31 Dec 2003


Oct 23 1999

Sept 23, 2002


Feb 12, 2000

Oct 30, 2001


April 1, 2000

Sept 21, 2001


June 23, 2000

April 1, 2002


Feb 24, 2001

May 23, 2002


July 11, 2001

July 12, 2003


Aug 15, 2001

April 11, 2002


Sept 23, 2001

May 9, 2003


Nov 21, 2001

Not cured upto 31 Dec 2003


April 12, 2002

July 12, 2003


June 13, 2002

Sept 23, 2003


Oct 3, 2002

Not cured upto 31 Dec 2003


Dec 12, 2002

Dec 23, 2003


Dec 16, 2002

Sept 1, 2003


Feb 12, 2003

Not cured upto 31 Dec 2003


Sept 1, 2003

Not cured upto 31 Dec 2003


Oct 11, 2003

Not cured upto 31 Dec 2003


Space for Exercise:


Measurement of Mortality:

Crude Death Rate: It is defined as “the number of deaths (from all causes) per 1000 estimated mid year population in one year, in a defined geographical area.

No. of deaths during the year Crude Death Rate = ------------------------------------x 1000 Mid year population

Specific Death Rates: can be specific to age, sex, occupation, diseases, etc.

Disease Specific Mortality: No. of deaths from specific disease during a calendar year Disease Specific = ------------------------------------------------ X 1000 Mortality Rate

Mid year population

Example: In a village with population of 5000 there are 5 deaths due to tuberculosis occurred in a year. Death rate due to tuberculosis would be 1 per 1000.


Child Mortality Still Birth Ratio: Defined as “ Death of foetuses weighing 1000 gm (this is equivalent to 28 weeks of gestations) or more occurring during one year in every 1000 live births.

Foetal deaths weighing 1000gm or more at birth Still Birth=------------------------------------------------------------- X 1000 Ratio

Total no of live births

Still Birth Rate: Still Birth Rate is defined as number of deaths of foetuses weighing 1000gm or more occurring during 1 year per 1000 total births (live + still births).


Foetal death weighing 1000gm or more at birth

Birth = --------------------------------------------------------------- X 1000 Rate

Total (live + still) births weighing 1000gm or more at birth

Neonatal Mortality Rate (NMR): NMR is defined as the number of neonatal deaths under 28 days of age in a given year per 1000 live births in that year

No of death of children under 28 days of age in a year NMR=------------------------------------------------------------------- x1000 Total live births in the same year

Post-neonatal Mortality Rate: It is defined as the ratio of post neonatal deaths (28 days to under one year) in a given year to the total number of live births in the same year, usually expressed as a rate per 1000. 36

No. of deaths of children between 28 days and one year of age in a given year PNMR = ------------------------------------------------------- X 1000 Total live births in the same year

Peri-natal Mortality Rate (PMR): It is defined as number of foetal deaths (28 weeks gestations & more) + early neonatal deaths (Ist week) in one year per 1000 live births in the same year Number of foetal deaths (28 weeks gestations & more) + Early neonatal deaths (Ist week) in one year PMR=-------------------------------------------------------------------X 1000 Live births in the same year

Infant Mortality Rate (IMR): Defined as the ratio of infant deaths in a given year to the total number of live birth in the same year, usually expressed as a rate per 1000 live births.

No. of deaths of children less than 1 year of age in a year IMR=----------------------------------------------------------------------X 1000 No. of live births in the same year

Under 5 Mortality Rate (U5MR): It is defined as annual number of deaths of children under 5 years of age expressed as a rate per 1000 live births.


No of deaths of children 5 years


Acute fever with altered sensorium


Acute fever with renal involvement

(vii) Acute flaccid paralysis in a child (viii) Acute fever with painful lymph node (ix)

Acute febrile severe illness of unknown aetiology.


Occurrence of two or more epidemiologically linked cases of meningitis.


Even a single case of measles or any other epidemic prone disease from a tribal or other poorly accessible area.

(xii) Unusual isolate (xiii) Shifting in age distribution of cases (xiv) High vector density (xv) Natural disasters. Steps of investigation of an Epidemic: 1.

Verification of the diagnosis by: a)

Clinical examination


Laboratory diagnosis

For clinical diagnosis, standard case-definitions of outbreak disease should be known to the medical officers.



Confirmation of the existence of an epidemic by: i. Cases finding through active surveillance and community surveys: During the period of the outbreak, all the cases of the disease under consideration occurring in that area should be identified and listed through active surveillance. ii. Visits or telephonic calls to the medical facilities or private practitioners, NGOs, key community representatives. iii. Active surveillance should be maintained even after the outbreak is over (till double the incubation period has elapsed after the last case). iv. In




assistants/volunteers may be enlisted for house-to-house visits. 3.

Line listing, defining and counting of cases: Persons who are

ill and meet the case definition for the outbreak disease should be line listed. This is a list of all reported cases with the relevant data on each case. The line list suggested for field use is given below:


Format for line listing

S. Name FatherAddress

Age Sex Symptoms Date Outcome Remarks

No of the/Husb .

of illness of


patien and’s

onset ill/recover





sympt oms

Note: A column on immunization status should be added for vaccine preventable diseases.


Description of outbreak


Distribution by time: by hours (e.g. in case of food poisoning), days, weeks or months as appropriate.


Distribution by place: map of the area.


Distribution by person e.g.(i) < 1 year, 1-4 yr, 5-14 yr – 44 yrs and > 45 yrs (ii)


Sex – male or female

Description of environmental conditions: e.g. rainfall, humidity, temperature, drinking water supply, environmental sanitation, etc.


Additional steps for VPDs Immunization coverage of various vaccines by: -



Performance records available at PHC /subcentre


Past vaccination coverage evaluation surveys.



Laboratory investigations:


Entomological investigations “in case of outbreaks of vector borne diseases” e.g. malaria, dengue fever/DHF etc.


Defining who is at risk of disease: e.g. in case of fever- age groups,


Follow up visits: are important for -

Detection of last cases.


Detection and treatment of complications


Evaluation of the control strategy


Complete the documentations of the outbreak.

12. Documentations A suggested format for final report is given in the chapter of Research methodology.

Exercise: Meerut district was reported to be affected by an “outbreak” of acute gastroenteritis (GE) in July-August, 2000. About 2270 cases and 413 deaths occurred during this period. Most of the cases had only diarrhoea and vomiting. Q.NO.1. How will you decide whether or not the district was in the grip of an outbreak? (Table-1 Describes the reported data on GE from the Meerut district during 1997-2000) Table 1 Cases and Deaths due to GE in district Meerut 1997-2000 Year No. of cases No. of deaths 1997 981 225 1998 375 112 1999 1387 173 2000 2380 426


Now, will you consider it an outbreak of GE? If yes why? If not, why? ________________________________________________________ ________________________________________________________

* Analysis of the age distribution of 308 deaths revealed that about 9% of deaths occurred in children below five years of age and about 62% of deaths occurred in adults above 20 years of age. Q.No.2. Does it help you in suspecting cholera as the cause of this outbreak? ________________________________________________________ ________________________________________________________


What was the most disturbing features in this outbreak? Was it preventable?

* Rectal swabs from 59 cases were examined in the laboratories of NICD, Delhi. 15 Samples were positive for V.cholerae O1 biotype E1 Tor. The isolates were sensitive to tetracycline, nalidixic acid, ampicillin and chloramphenicol, but resistant to furazolidone and streptomycin. The other samples were found negative for any enteropathogens. Q.No.4. What are the possible reasons for 44 of 59 samples being found negative for enteropathogens? ________________________________________________________ ________________________________________________________ Q.No.5. Assume yourself as the team leader for the investigation of this outbreak. (i) How will you plan the investigations? (ii) How will you control the outbreak? ________________________________________________________ ________________________________________________________



Surveillance of diseases is the continuing scrutiny of all aspects of the occurrence and spread of a disease that are pertinent to effective control.

Communicable diseases constitute a significant disease

burden and are major causes of morbidity, mortality and long-term severe mental and physical disabilities. Many of these diseases are epidemic prone.

The frequency of the occurrence of the epidemics is an indication of the inadequacy of the surveillance system and preparedness to identify and control outbreaks in a timely manner.

Surveillance is data collection for action. Surveillance data are required for planning disease activities and for evaluating impact. Disease surveillance data are also required to identify high-risk areas or high-risk age specific and other groups who require special attention. Early warning signals will be missed in the absence of an effective surveillance system.

To plan any disease control programme and to identify and control outbreaks, it is important to know the following:  Who get the diseases  How many get them  Where they get them  When they get them  Why they get them There are five steps in the surveillance procedure, which must be carried out at each level, starting from the Primary Health Centre 58

(PHC). Each level must have the capacity for analysing and control of outbreaks. The five recommended steps are:  Collection of data  Compilation of data  Analysis and interpretation  Follow up action  Feedback

Prerequisites for effective surveillance Prerequisite for effective surveillance are:  Use of standard case definitions  Ensuring regularity of the reports  Action on the reports For developing an effective disease surveillance system, the district health officer / PHC medical officer must also be clear about:  What information to gather  How often to compile and analyse the data  How often and to whom to report  What proforma or formats to use  What action to take The data collected should be uniform, regular and timely. Standard case definitions are important to ensure uniformity in reporting so that all reporting units use the same criteria for reporting cases. It is also important to have a list of all reporting units so that the regularity and timeliness of the reports is checked. If no cases are seen, a nil report should be submitted. All levels in the system must:  have the standard case definitions  have a list of all reporting units


 monitor receipt of reports in time  monitor completeness of reports The standard case definition of diseases has been given in a NICD manual. The cases have been classified as:  Suspect – diagnosis made on the basis of history by paramedical personnel and members of the community  Presumptive – diagnosis made on typical history and clinical examination by a medical officer  Confirmed – clinical diagnosis by a medical officer and / or positive laboratory identification

Regularity of reports Monitoring the regularity of surveillance reports is an important function of the surveillance system. A list of all reporting units in the area must be kept. The Chief Medical Officer of Health of the district must identify the reporting units. Besides the PHCs and Community Health Centre (CHCs), hospitals, large dispensaries and clinics should be included as reporting units.

Frequency of reporting A system of monthly reporting of disease and programme specific data already exists in the districts. The routine reporting of cases and deaths should continue.

Methods of data collection Several methods can be used for collecting data.

While routine

reporting (passive surveillance) is, universalized, other methods are need and area specific. These include:


 Sentinel surveillance  Active surveillance (active search for cases)  Vector surveillance  Laboratory surveillance  Sample surveys  Outbreak investigations  Special studies

Routine reporting (institutional based or passive reporting) All the national health programmes require that the cases and deaths recorded in the out-patient or in-patient departments of hospitals, dispensaries, community health centres, primary health centres and other health facilities manned by a medical officer are reported to the local health authority on a monthly basis. The consolidated report of the district is forwarded to the state health officer. For some national programmes, a copy of the district report is also forwarded to the concerned officer at the central level.

At each level in the system, the report is required to be analysed and appropriate action taken as indicated. The reports should be checked for completeness and regularity as these factors can influence the analysis of the reports.

Sentinel surveillance A sentinel surveillance system is developed to obtain more reliable and extensive disease information than is available through the routine reporting. A hospital, health centre, laboratory or a rehabilitation centre, which caters to a relatively large number of cases of the


disease, can be considered as a sentinel centre. A sentinel centre can provide information on one or more disease.

Since the sentinel centres are carefully selected and because the number of the reporting units is much smaller, it is easier to maintain the quality and regularity of the reports.

There should be a close liaison between the sentinel centre and the local health office. The sentinel centre can help in providing:  Line lists of cases of selected diseases which is essential for epidemiological analysis  Early warning signals, which should trigger action for outbreak investigations.

Active surveillance However good the routine reporting system, there will still be cases that will not be recorded under this system. Patients with mild or moderate severity may not seek treatment and some may go to private practitioners. It is also possible that patients in severe condition are taken directly to a large hospital in another district for specialized care. Some cases may die within a short period of onset of symptoms without receiving care at a health facility such as cases of neonatal tetanus.

Active surveillance or active search for cases is resource intensive. The decision to start active surveillance depends on many factors and ground situations.

Active search may be called for under the

following circumstances:


 During outbreaks to determine the extent of the outbreak and keep mortality rates low by initiating early treatment. Active surveillance is carried out to know the magnitude of the problem, which will help in planning logistics for control. In addition, it will give baseline data to evaluate control strategy. It also helps in understanding the genesis of the outbreak.  As the number of cases of a disease decline to negligible levels and it becomes important to receive information on every single case as quickly as possible so that further transmission is interrupted by initiating outbreak control measures.


example, active surveillance is recommended for acute flaccid paralysis (AFP).  To trace cases and contacts over a limited period of time for selective interventions to interrupt transmission. This strategy is recommended in the yaws affected districts.  To confirm the absence of even a single case. This is done during the pre-certification phase for disease eradication, as ‘zero’ incidence has to be maintained for a period of three years. During field visits by the supervisors, absence of disease can be confirmed by contacting few key persons such as a school teacher, Gram Pradhan, Anganwadi Worker and others.

Vector surveillance Vector surveillance is important to monitor the existing vectors in the area. Increase in the density of the vectors or their breeding sites should be taken as early warning signals for vector borne outbreaks. Aedes mosquito, the vector for dengue fever, prefers artificial collection of water for breeding (for e.g. Desert coolers, cement tanks, 63

broken unused pots, tyres etc.). A house index of 10% or more indicates potential for outbreak of dengue / Dengue Haemorrhagic Fever (DHF). The clues mosquitoes breed in dirty and polluted water, whereas anopheles prefers clean water for breeding.

Laboratory surveillance Testing water samples for Coliform organisms is a measure to determine the risk of water borne outbreaks.

Water quality

monitoring is recommended in vulnerable pockets and from sources supplying drinking water to a large population. Checking the chlorination levels of the water is also important, especially during the monsoon and post-monsoon periods.


measures by the health department are precautionary measures in addition to the mandatory requirements of the concerned departments.

Laboratory surveillance must be stepped up in anticipation or in the event of an outbreak. Serological and other laboratory based surveys are sometimes conducted as research projects to collect baseline prevalence rates or to identify high risk factors, age-groups or population sub-groups.

Presentation of Data: The data that is collected is presented using tables, diagrams, pictures, and maps for easy understanding. You should look for spikes, clusters, trends, and systematic variations. Spike: Unusual or sharp increase (as in outbreaks) or decrease in number of cases. Clusters: Grouping of cases.


Trends: Gradual increase or decrease in cases over time.

Exercise 1: Construct appropriate diagram for presentation of following data. 1: In a community in a particular year the numbers of cases reported due to various diseases are as follows: Fever Diarrhoea Conjunctivitis Scabies Measles

225 415 283 78 12

Exercise 2: Year-wise distribution of measles and diabetes cases for last ten years is as follows. Year









660 190

179 547

123 79 89 101




289 298

306 407

476 469 507 508

Discuss it with your Facilitator







Annexure 1: Proportion of various age groups in India: Eligible couples: Pregnant women: live births) Infants:

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