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MEDICINE AND PHARMACY FACULTY UNIVERSITY OF ORADEA EPIDEMIOLOGY By CONSTANTA TURDA, M.D.

MEDICINE AND PHARMACY FACULTY UNIVERSITY OF ORADEA EPIDEMIOLOGY By CONSTANTA TURDA, M.D. History of Epidemiology. Hippocrates (460-377 B.C.). On Airs, Waters, and Places Idea that disease might be associated with physical environment. Thomas Sydenham (1624-1689).

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MEDICINE AND PHARMACY FACULTY UNIVERSITY OF ORADEA EPIDEMIOLOGY By CONSTANTA TURDA, M.D.

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  1. MEDICINE AND PHARMACY FACULTYUNIVERSITY OF ORADEAEPIDEMIOLOGY ByCONSTANTA TURDA, M.D.

  2. History of Epidemiology

  3. Hippocrates (460-377 B.C.) • On Airs, Waters, and Places • Idea that disease might be associated with physical environment

  4. Thomas Sydenham (1624-1689) • Recognized as a founder of clinical medicine and epidemiology • Emphasized detailed observations of patients & accurate recordkeeping

  5. James Lind (1700’s) • Designed first experiments to use a concurrently treated control group

  6. Edward Jenner (1749-1823) • Pioneered clinical trials for vaccination to control spread of smallpox  • Jenner's work influenced many others, including Louis Pasteur who developed vaccines against rabies and other infectious diseases

  7. Ignas Semmelweis (1840’s) • Pioneered handwashing to help prevent the spread of septic infections in mothers following birth 

  8. John Snow (1813-1858) • Father of epidemiology • Careful mapping of cholera cases in East London during cholera epidemic of 1854 • Traced source to a single well on Broad Street that had been contaminated by sewage

  9. History of Epidemiology (Cont’d) • Vital Statistics • John Graunt (1620-1674) • William Farr (1807-1883) • Occupational medicine & Industrial Hygiene • Bernardino Ramazzini (1633-1714) • Role of carriers in transmission • Typhoid Mary & George Soper

  10. Typhoid Mary & George Soper • Mary Mallon, a cook responsible for most famous outbreaks of carrier-borne disease in medical history • Recognized as carrier during 1904 N.Y. typhoid fever epidemic • When source of disease was traced, Mary had disappeared only to resurface in 1907 when more cases occurred • Again Mary fled, but authorities led by George Soper, caught her and had her quarantined on an island • In 1910 the health department released her on condition that she never accept employment involving the handling of food • Four years later, Soper began looking for Mary again when two new epidemics broke out; Mary had worked as a cook at both places • She was found and returned to North Brother Island, where she remained the rest of her life until a paralytic stroke in 1932 led to her slow death, six years later

  11. Typhoid Mary

  12. U.S. History of Epidemiology • Lemuel Shattuck (1850) • Proposed creation of a permanent statewide public health infrastructure • Recommended establishing state & local health offices to gather statistical information on public health conditions • Quarantine Commissions (1857) • 1st Public Health Book (1879) • U.S. Public Health Service founded (1902) • Pure Food and Drug Act (1906) • Pasteurization of milk (1913) • 1st School of Public Health (1913)

  13. Historic Aspects of the Development of Morbidity Statistics in the U.S. • Edgar Sydenstricker (Early 1900’s) • Pioneer public health statistician • Three notable studies: • Tuskegee syphilis study (1932-1970) • Framingham heart study (1948-present) • Epidemiology of cigarette smoking (1950’s - present)

  14. Modern History of Epidemiology in the U.S. • Mortality stats in first half of century • Unstable because of outbreaks of infection • Stats reversed by 1950’s because of childhood immunizations, medical interventions and public health measures • Economic growth reduced squalor • Introduction of antibiotics in 50’s

  15. Wake-up Calls • Over-optimism in 60’s and 70’s • AIDS recognized • Cholera in the southern hemisphere • Legionnaire’s disease • New forms of hepatitis • Chlamydia and heart disease • Hospital acquired infections • Antibiotic resistance

  16. U.S.Mortality Index (annual deaths/100,000) • 1900 - 500 • 1918-1919- 850 • Mid-century-1982 - 30 • 1982-1994 - 60

  17. Future Challenges • Instant global transmission of pathogens • Population overcrowding • Ease of travel • Importation of foods

  18. DEFINITIONS • What is epidemiology? • What is an epidemiologist?

  19. EPIDEMIOLOGY is the study of the nature, cause, control and determinants of the frequency and distribution of disease, disability, and death in human populations.Epidemiology:the study of factors influencing the occurence, transmission, distribution, prevention and control of disease in a defined population

  20. An EPIDEMIOLOGIST is a public health scientist, who is responsible for carrying out all useful and effective activities needed for successful epidemiology practice

  21. Methods of Epidemiology • Public Health Surveillance • Disease Investigation • Analytic Studies • Program Evaluation

  22. Terminology • Endemic • Hyperendemic • Holoendemic • Epidemic • Pandemic • Epizootic • Incidence • Prevalence Terms used for reference to various forms of outbreaks

  23. Endemic:a disease or pathogen present or usually prevalent in a given population or geographic region at all times Hyperendemic:equally endemicin all age groups of a population Holoendemic:endemicin most of the children in a population, with the adults in the same population being less often affected Epidemic:a disease occuring suddenly in numbers far exceeding those attributable to endemic disease; occuring suddenly in numbers clearly in access of normal expectancy Pandemic:a widespread epidemic distributed or occuring widely throughout a region, country, continent, or globally Epizootic:of, or related to a rapidly spreading and widely diffused disease affecting large numbers of animals in a given region

  24. Incidence:rate of occurrence of an event; number of new cases of disease occuring over a specified period of time; may be expressed per a known population size Prevalence:number of cases of disease occurring within a population at any one given point in time

  25. Terms Associated with Disease Causation, etc. • Host • Agent • Environment • Fomites • Vector • Carrier – active • Incubatory • Convalescent • Healthy • Intermittent Your Assignment: Define these terms

  26. Changing Patterns of Community Health • Health patterns in constant state of flux • Infectious versus chronic diseases • Population and age-related

  27. Chain of Infection • Etiological agent • Source/Reservoir • Portal of exit • Mode of transmission • Portal of entry • Susceptible host

  28. Classification of Microorganisms • Viruses • •RNA–DNA • • RNA viruses genetically unstable • •Lipid enveloped–nonenveloped • • Solvent-detergent treatments virucidal only for enveloped viruses • Bacteria • •Gram-positive–gram-negative•Antibiotic sensitivity differs • • Diagnostic and therapeutic uses of gram-negative capsule • Fungi • •Disseminated vs. superficial • •Mold vs. biphasic • Parasites • •Complete cycle • •Larval migrans • Prions • •Pathogenesis unclear • •Resistant to disinfection

  29. A Clinician’s View • Diseases classified according to signs and symptoms: • 1. Diarrheal diseases • 2. Respiratory diseases • 3. Cutaneous/soft tissue infection • 4. CNS diseases • 5. Septicemic diseases • 6. Fever of undetermined origin

  30. Modes of Transmission • Contact transmission • Vehicle transmission • Vector transmission

  31. An Epidemiologist’s ViewMeans of Spread of Infectious Diseases • Contact • •Direct • •Indirect•Fomites • • Body secretions (blood, urine, saliva, etc.) • Vector • Airborne • •Small-particle aerosol

  32. Some Infectious Diseases Spread by Contact • Salmonellosis • 2. Campylobacter • 3. Shigellosis • 4. Clostridium perfringens food poisoning • 5. Staphylococcal enterotoxin food poisoning • 6. Cholera • 7. Giardiasis • 8. Listeriosis

  33. Some Important Food- and Waterborne Infections • Salmonellosis • 2. Campylobacter • 3. Shigellosis • 4. Clostridium perfringens food poisoning • 5. Staphylococcal enterotoxin food poisoning • 6. Cholera • 7. Giardiasis • 8. Listeriosis

  34. Some Important Airborne Infections • 1. Tuberculosis • 2. Influenza • 3. Childhood Infections • − Measles, mumps, rubella, pertussis • 4. Parainfluenza • 5. RSV • 6. Legionella

  35. Some Important Vectorborne Infections • 1. Malaria • 2. Viral encephalitis • − SLE, WEE, EE, VE, California virus • 3. Schistosomiasis • 4. Tularemia • 5. Dengue • 6. Yellow fever • 7. Rocky Mountain spotted fever • 8. Leishmaniasis • 9. Trypanosomiasis

  36. Reservoirs of Infectious Diseases • 1. Human • 2. Animal (zoonoses) • 3. Soil • 4. Water

  37. Some Infectious Diseases with a Human Reservoir • 1. AIDS (HIV infection) • 2. Syphilis • 3. Gonorrhea • 4. Shigellosis • 5. Typhoid fever • 6. Hepatitis-B virus • 7. Herpes simplex virus

  38. Some Diseases with an Animal Reservoir (Zoonoses) • 1. Nontyphoidal salmonellosis • 2. Brucellosis • 3. Anthrax • 4. Listeriosis • 5. Viral encephalitis (SLE,WEE, CEE) • 6. Rabies • 7. Plague

  39. Some Important Diseases with a Soil Reservoir • 1. Histoplasmosis • 2. Coccidioidomycosis • 3. Blastomycosis • 4. Tetanus • 5. Botulism

  40. Some Infectious Diseases with a Water Reservoir • 1. Pseudomonas infections • − Sepsis, UTI, “hot tub” folliculitis • 2. Legionnaires’ disease • 3. Melioidosis

  41. Some Infectious Diseases Spread by Contact • Sexually transmitted diseases • − Syphilis, gonorrhea, chlamydia, AIDS • 2. Staphylococcal infections • 3. Streptococcal infections • 4. Many nosocomial infections • 5. Rhinovirus colds • 6. Brucellosis (slaughter house contact) • 7. Hepatitis B virus infection

  42. Classes of Epidemics • Common source (vs. sporadic) • Point source • Intermittent • Continuous • Propagated Your Assignment: Define these terms & identify which apply to the following three graphs

  43. Infectious Agents: 3 Important Epidemiologic Properties • 1. Infectivity • − The propensity for transmission • − Measured by the secondary attack rate in a household, school, etc. • 2. Pathogenicity • − The propensity for an agent to cause disease or clinical symptoms • − Measured by the apparent : inapparent infection ratio • 3. Virulence • − The propensity for an agent to cause severe disease • − Measured by the case fatality ratio

  44. Infectious Agents: 3 Important Epidemiologic Properties • Incubation period = The period between exposure to the agent and onset of infection (with symptoms or signs of infection) • Secondary attack rates = The rates of infection among exposed susceptibles after exposure to an index case, such as in a household or school

  45. Definitions of Some Relevant Terms (cont.) • 􀂄Inapparent(or subclinical infection)− An infection with no clinical symptoms, usually diagnosed by serological (antibody) response or culture • 􀂄Immunity− The capacity of a person when exposed to an infectious agent to remain free of infection or clinical illness • 􀂄Herd immunity− The immunity of a group or community. The resistance of a group to invasion and spread of an infectious agent, based upon the resistance to infection of a high proportion of individual members of the group. The resistance is a product of the number of susceptibles and the probability that those who are susceptible will come into contact with an infected person.

  46. Definitions of Some Relevant Terms (cont.) • 􀂄Persistent infection− A chronic infection with continued low-grade survival and multiplication of the agent • 􀂄Latent infection− An infection with no active multiplication of the agent, as when viral nucleic acid is integrated into the nucleus of a cell as a provirus. In contrast to a persistent infection, only the genetic message is present in the host, not viable organisms.

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