LESSON 1: CONTRIBUTIONS OF EPIDEMIOLOGISTS

• CONTRIBUTIONS OF EPIDEMIOLOGISTS

  1. Investigating epidemics and new diseases
  2. Studying the biologic spectrum of disease
  3. Surveillance of community
  4. Setting disease control priorities
  5. Improving diagnosis, treatment, and prognosis of clinical diseases.
  6. Improving health services research
  7. Providing expert testimony in courts of law
• epidemiologists often have provided the initial hypotheses about disease causation for other scientists to test in the laboratory.
• Knowledge of the modes of transmission led epidemiologists to suggest ways to prevent each of these diseases
• The rapid growth in world population; increased travel and contact with new ecosystems, such as rain forests; declining effectiveness of antibiotics and insecticides; and many other factors encourage the development of new diseases or the resurgence of previous disorders.
• This variation in the severity of a disease process is known as the biologic spectrum of disease, or the iceberg phenomenon.
• The iceberg phenomenon is paramount to epidemiology, because studying only symptomatic individuals may produce a misleading picture of the disease pattern and severity. The biologic spectrum also applies to viral disease.
• The latter term is appropriate because most of an iceberg remains unseen, below the surface, analogous to asymptomatic and mild cases of disease.
• This is an example of iceberg phenomenon: The diphtheria outbreak caused two deaths; symptoms of clinical illness in 12 children who recovered; and asymptomatic infection in 32 children, some of whom had even been immunized against diphtheria. The 32 cases of asymptomatic infection were discovered by extensive culturing of the throats of the school-age children in the outbreak area. In this iceberg. 14 infections were visible, but the 32 asymptomatic carriers would have remained invisible without extensive epidemiologic surveillance.
• Randomized trials of preventive measures in the field (field trials) are an important phase of evaluating a new vaccine before it is given to the community at large.
• Field trials, however, are only one phase in the evaluation of immunization programs. After a vaccine is introduced, ongoing surveillance of the disease and vaccine side effects is essential to ensure the vaccine’s continued safety and effectiveness.
• As part of its response plan, the U.S. now has a stockpile of smallpox vaccines sufficient to vaccinate everyone in the country in the event of a smallpox emergency. Epidemiologists are thus contributing to national security by helping to establish new approaches to surveillance (syndromic surveillance)
• Disease control priorities should be based not only on the currently existing size of the problem, but also on the potential of a disease to spread to others; its likelihood of causing death and disability; and its cost to individuals, families, and the community.
• The application of epidemiologic methods to clinical questions helps us to improve clinical medicine, particularly in the diagnosis, therapy, and prognosis of disease. This is the domain of clinical epidemiology.
• Diagnosis is the process of identifying the nature and cause of a disease through evaluation of the clinical history, review of symptoms, examination or testing.
• Epidemiologic methods are used to improve disease diagnosis through the selection of the best diagnostic tests, the determination of the best cutoff points for such tests, and the development of strategies to use in screening for disease.
• This is an example of treatment: One study used a randomized controlled clinical trial in many U.S. centers to test the hypothesis that pharmaceutical therapy with methylprednisolone reduced spinal cord damage and improved residual motor function after acute spinal cord injury.
• Epidemiologic methods also help improve our understanding of a patient’s prognosis, or probable course and outcome of a disease.
• This is an example of prognosis: Patients and families want to know the likely course of their illness, and investigators need accurate prognoses to stratify patients into groups with similar disease severity in research to evaluate treatments.
• This is an example of risk estimation: Epidemiologic methods permit risk estimation. These are perhaps best developed in various cardiac risk estimators using data from the Framingham Heart Study.
• The principles and methods of epidemiology are used in planning and evaluating medical care.
• In health planning, epidemiologic measures are employed to determine present and future community health needs. Demographic projection techniques can estimate the future size of different age groups. Analyses of patterns of disease frequency and use of services can estimate future service needs. Additional epidemiologic methods can be used to determine the effects of medical care in health program evaluation as well as in the broader field of cost-benefit analysis.
• Therefore, expert medical testimony often requires a high level of epidemiologic expertise.
• 1. The many types of lawsuits that may rely on epidemiologic data include those involving claims of damage from
  2. general environmental exposures (e.g., possible association of magnetic fields or cellular phone use and brain cancer)
  3. occupational illness claims (e.g., occupational lung damage from workplace asbestos), medical liability (e.g., adverse effects of vaccines or medications),
  4. product liability (e.g., association of lung cancer with tobacco use, of toxic shock syndrome with tampon use, and of cyclooxygenase-1 inhibitor medications with cardiovascular disease)