Subject: Epidemiology And Bio-statistic.

B.Sc in Nursing 3rd year And Diploma in Nursing  


Epidemic like diseases do not occurs by chance they require that a harmful agent comes into contact with group of susceptible host in the proper environment.

Objectives of an epidemic investigation:

Objectives of an epidemic investigation are given bellow-

  1. To define the magnitude of the epidemic outbreak or involvement in terms of time, place and person.
  2. To determine the particular conditions and factors responsible for the occurrence of the epidemic.
  3. To identify the cause, source of infection, and mode of transmission to determine measure necessary to control the epidemic.
  4. To control continuing outbreak.
  5. To prevent future outbreak.
  6. To strengthen surveillance at local level.
  7. To advance knowledge about a disease.
  8. To provide training opportunities.

Basic steps of an epidemic investigation

  1. Verification of disease- It is the first step in epidemic investigation verification is carried out by laboratory test.
  2. Confirmation of the existence of an epidemic.
  3. Defining the population at risk.
  4. Rapid search for all cases and their characteristics.
  5. Evaluation of ecological factors.
  6. Further investigation of population at risk.
  7. Data analysis.
  8. Develop a hypothesis.
  9. Testing the hypothesis.
  10. Formulate a hypothesis or writing the report.

Explanation, the basic steps in conducting investigation are:

  • Verification of disease:  It is the first step in epidemic investigation. Verification are carried out by-
  1. Laboratory test
  2. Clinical criteria may be used when laboratory results are unreliable
  • Confirmation of the existence of an epidemic:
  1. Look for unreported case that may be part of the outbreak of the disease
  2. Determine the population at risk for developing the disease
  3. Compare the incidence of disease in the population now with previous time period
  • Defining the population at risk:
  1. Obtaining the map of the area
  2. Counting the population
  • Rapid search of all cases and their characteristics:
  1. Identification of cases by medical survey
  2. For collecting data from the cases epidemiological case sheet can be used
  3. Searching for more cases – it can be getting from the patients, their relatives or attendants
  • Evaluation of the etiological factors: Such as sanitary status of the eating place, water and milk supply, environment condition etc
  • Further investigation of population at risk: Such as medical examination, screening test, examination of food, faces, blood samples, assessment of immunity status
  • Data analysis : Analysis the data by age, sex, occupation and other risk factors
  • Develop a hypothesis: A hypothesis is a supposition arrived from observation. An epidemiological hypothesis should specify
  1. Population
  2. The specific cause of the disease
  3. The expected outcome of the disease
  • Testing the hypothesis
  • Formulate a conclusion



Surveillance may be defined as regular and systematic collection of data on the disease incidence for the purpose of taking appropriate action.

Public Health Surveillance

Public health surveillance is the mechanism that public health agencies use to monitor the health of their communities.Its purpose is to provide a factual basis from which agencies can appropriately set priorities, plan programs, and take actions to promote and protect the public’s health.

Objectives of surveillance

  1. Monitoring trends and estimate magnitude of health Problem.
  2. Epidemic (outbreak) detection and prediction.
  3. Monitoring progress towards a control objective.
  4. Timely implementation of effective control measures.
  5. Monitoring programme performance.
  6. Detecting changes in the trend/ distribution of the endemic disease.
  7. Estimating future disease impact.
  8. Evaluating an intervention.
  9. Understanding characteristics of health events.
  10. Facilitating planning.

Types of surveillance

  • Passive surveillance occurs when data are routinely collected and forwarded.
  • Active surveillance occurs when data are sought out by visiting or contacting a reporting site.
  • Sentinel surveillance in the community from house to house. It occurs when only selected sites report data. This is rarely representative of the population but can be used to monitor trends and collect more detailed information. The network of physicians reporting influenza-like illness, described above, is an example of sentinel surveillance.
  • Laboratory surveillance when based from laboratories.
  • Epidemiological surveillance
  • Environmental surveillance
  • Vector or serological surveillance.
  • Sample survey
  • Demography surveillance
  • Nutritional surveillance

Surveillance functions:

Core function

  • Reporting
  • Detection
  • Investigation & confirmation
  • Analysis & interpretation
  • Action / response

Support function

  • Training
  • Supervision
  • Resources
  • Standards / guidelines

Disease to be kept under surveillance

  1. Disease are national programme e.g. malaria, TB, AIDS, polio.
  2. Disease capable of causing outbreak e.g. measles, cholera, chiken pox.
  3. High cases fatality rate e.g. tetanus, TB, rabies
  4. Transmitted through vector or vehicle e.g. typhoid fever, dysentery
  5. Significant disease burden e.g. cancer, AIDS
  6. Can cause prolong mental and physical disability e.g. accident, chronic disease
  7. Amenable to control through effective means.

Steps in planning a surveillance system

  • Establish objectives
  • Develop case definition
  • Determine data source or data collection mechanism
  • Develop data collection instrument
  • Field-test methods
  • Develop and test analytic mechanism
  • Develop dissemination mechanism
  • Assure use of analysis and interpretation.



 Baby Kirttania,