Question

Why do EOH practitioners (The Environmental and Occupational Health) need a firm grasp of basic epidemiological principles in their daily work? Integrate specific examples and supportive backing for your response

Answer 1

Public health workers use epidemiologic principles as the foundation for disease surveillance and investigation activities.

Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.

Every public health worker should be familiar with the basic principles in this definition and how they are useful.

• Distribution - Epidemiology is concerned with the frequency and pattern of health events in a population. Frequency includes not only the number of events in a population, but also the rate or risk of disease in the population. Determining the rate of disease occurrences (number of events divided by size of the population) is critical for making valid comparisons across different populations.
• Determinants - Epidemiology is also used to search for causes and other factors that influence the occurrence of health-related events. The occurrence of a health-related event is usually related to multiple determinants that should be considered. Examples of determinants include host susceptibility to a disease, and opportunity for exposure to a microorganism, environmental toxin, insect vector or other infected individual that may pose a risk for acquiring disease.
• Specified populations - Epidemiologists are concerned with the collective health of people in a community or other area and the impact of health events on that population.
• Application - Epidemiology provides data for directing public health action. An epidemiologist uses the scientific methods of descriptive and analytic epidemiology in "diagnosing" the health of a community, but also must call upon experience and creativity when planning how to control and prevent disease in the community.

Disease surveillance usually begins with descriptive epidemiology -- defining the what, who, when and where of health-related events.

• what - Define the disease events and/or its determinants
• who - Descriptions of demographic characteristics are helpful in determining which groups are at risk for some outcome. The demographic characteristics usually include age, sex and race/ethnicity. Other categories include socioeconomic status, history of occupation, or smoking habits, which provide useful information about exposures that may present a risk. A history of underlying diseases may be useful for determining susceptibility to certain conditions.
• when - Following changes in disease rates over time, following long-term disease trends and knowledge of the seasonality of certain diseases helps identify unusual occurrences that may define epidemics. Temporal associations between particular exposures on illness give information about incubation periods and exposures posing a risk to others.
• where - Insight into the geographical extent of health-related events gives an idea of where the agent that causes a disease normally lives and multiplies, what may carry or transmit it and how it spreads.

The Primary Applications of Epidemiology in Public Health

To set policy and plan programs, public health officials must assess the health of the population they serve and must determine whether health services are available, accessible, effective and efficient. Epidemiology provides data for directing public health action. The information is used when planning how to control and prevent disease in the community. Through public health surveillance, a health systematically collects, analyzes, interprets and disseminates health data on an ongoing basis. By knowing the ongoing pattern of disease occurrence and disease potential, a health agency can effectively and efficiently investigate, prevent and control disease in the community.

Uses of Epidemiology

• Count health-related events
• Describe the distribution of health-related events in the population
• Describe clinical patterns
• Identify risk factors for developing diseases
• Identify causes or determinants of disease
• Identify control and/or preventive measures
• Establish priorities for allocating resources
• Select interventions for prevention and control
• Evaluate programs
• Conduct research
  • risk factors and causes
  • drug trials / vaccine trials
  • operational research

  • Case Management

  • Verify the Diagnosis: It is very important to promptly establish or verify the etiologic agent responsible for the disease. For many diseases reported by physicians or others, there are often little or no laboratory data initially available to verify the diagnosis. Since control efforts depend on the exact diagnosis, it is important to: (a) determine if this information exists; (b) arrange for laboratory tests if the information does not otherwise exist; or (c) make the best guess about diagnosis if it cannot be obtained.
  • Determine if the Case is Infectious or Possibly Infectious: If the case is still infectious, you must identify available measures for preventing transmission. There are two ways to assess the case's infectivity:
    • estimation--uses the date of onset of illness, dates of known treatment, and known periods of infectiousness for an illness. For example, hepatitis A is no longer infectious after 1 week of the onset of symptoms. Strep throat is no longer infectious after 24 hours of treatment.
    • verification--requires laboratory testing of specimens for the case (for example, a stool specimen for a foodhandler with salmonellosis). Which method you use depends upon the disease (the period of communicability for some diseases is precise; for others it is not precise), the quality of information about the case (e.g., is date of onset known?), and the need to know definitely whether the case is infectious.
      In practice, because of delays in diagnosis and reporting, many cases will have passed the infectious stage by the time they are reported. In this instance, the opportunity to prevent transmission is lost, but preventive efforts can be directed to the case's contacts, and other purposes of case investigation can be fulfilled. You may need to contact the physician to fill in information about the case, determine results of laboratory tests, or arrange for tests. Also ask about similar cases for which a report may be pending.
  • Minimize the Duration of the Case's Infectivity: Drugs (antimicrobials) are the most important means to shorten the duration of infectivity for many diseases. Usually, decisions about drug treatment will be made by the time you investigate. However, sometimes it may be necessary to work with the patient and physician to ensure the patient is appropriately treated.
  • Put into Effect Practices for Preventing Transmission: These practices depend upon the disease and other circumstances. If the disease warrants, the case may have to employ these practices while ill and for a period after recovery during which (s)he is still infectious:
    • disinfect and dispose of contaminated material (e.g., blood, saliva, feces, urine, eating utensils, bedding, clothes, toys, etc.)
    • disinfect the case, clothing, bedding, etc. (e.g., lice)
    • encourage behavioral practices of the case (e.g., handwashing, covering the nose and mouth when coughing/sneezing, protecting lesions from contact with another person. Also, there may be a need for changes if individual is a foodhandler.)
    • isolate the case -- the duration and degree depends upon the illness