Steps of Investigation of Epidemic Disease

An epidemic's existence always presents a challenge to the national health administrations for its control and prevention since it throws the balance between agent, host, and environment off by a large amount. The study of epidemics benefits greatly from the application of epidemiology. An investigation of an epidemic's goals are:

• To quantify the size of an epidemic outbreak or involvement in terms of time, location, and individual.
• To identify the specific circumstances and causes behind the development of disease.
• To determine the steps required to control the epidemic, it is important to understand the cause, the source of the infection, and the routes of transmission.
• To offer suggestions for preventing recurrence.

The steps of investigation are

• Verification of diagnosis
  • The initial step is to as quickly as possible confirm the diagnosis on the spot. Clinical evaluation of a few straightforward cases might be sufficient, although laboratory tests might be confirmatory. False or fictitious reporting that may result from the general public misinterpreting symptoms and indicators is not included.
• Confirmation of the existence of an epidemic
  • When the number of the expected frequency for that population, based on prior experience, is present, it is considered to be an epidemic. While the existence of some epidemics, such as cholera, food poisoning, hepatitis A, etc., is frequently obvious and does not require comparison, the existence of more contemporary epidemics, such as cancer and cardiovascular diseases, does.
• Defining the population at risk
  • The population and number of homes in the area can be counted using a current, accurate map of the area. then choosing the proper denominator Attack rates and "population at risk" can be computed.
• Rapid search
  • A case definition may be formulated for rapid search of all cases. The number of cases in an area can be calculated by:
    • Medical survey: Identify all cases, including those who have not sought medical care and those possibly exposed to risk, by screening or by asking question.
    • Epidemiological case sheet: It is the case interview form to collect information from cases & exposed ones.
    • Searching of new case: The patient may be asked if he knew the other cases in the home, family, neighborhood, school, work place having an onset within the incubation of index case. Case admitted to local hospital should also be taken.
• Evaluation of the ecological factors
  • Investigations should be conducted into the ecological factors that contributed to the epidemic, such as the hygienic state of the food, milk, and water supplies, the establishment, water supply system breakdown, population movements, atmospheric changes like temperature, humidity, and air pollution, and the population, dynamics, and animal and insect reservoirs.
• Further investigation of population at risk
  • After the hypothesis has been established, more information may need to be gathered from the population at risk or a sample of it through medical examination, screening tests, study of feces or blood samples, biochemical studies, immunological status evaluation, etc. This will make it easier to tell who was exposed and if they are sick or not.
• Formulate the hypothesis
  • On the basis of time, place and person distribution or the agent, host and environment model, a hypothesis is formulated in terms of:
    • Possible source
    • Causative agent
    • Possible modes of spread
    • Environmental factors responsible
  • The formulated hypothesis should guide further investigation.
• Data analysis
  • The information gathered in this way is continually examined using the traditional criteria of time, place, and person. The Agent- Host- Environment model is set up for known agents. Based on common traits in the cases, it enables the source or risk factor to be identified.
    • Time: An epidemic curve is constructed and time clustering of cases is noted. An epidemic curve may suggest time relation with exposure to suspected factor, whether it is a common source or propagated epidemic and whether it is seasonal or cyclic trend.
    • Place: A spot map of cases (geographical distribution) is prepared & if possible, their relation to possible sources of infection. Clustering of cases may indicate a common source of infection.
    • Person: A person is analyzed in terms of age, sex, occupation and other possible risk factors. Attack rates, case fatality rates are calculated.

• Writing the reports
  • Finally, a thorough, accurate, and convincing report about the disease researched in a practical and scientific manner is written, including the background, historical data, methodology, analysis of data, and control measures. There may also be recommendations for the control and prevention of future instances of diseases of a similar nature.