1. Introduction to Epidemiology
BIOL 309
CSUSM
Fall 2017

2. Outline History of Epidemiology Basic Concepts and Terminology
Disease Transmission
Morbidity and Mortality

3. Outline History of Epidemiology Basic Concepts and Terminology
Disease Transmission
Morbidity and Mortality

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

5. “ And in particular, as the season and the year advances, he can tell what epidemic diseases will attack the city…….”

6. Thomas Sydenham ( )
Recognized as a founder of clinical medicine and epidemiology
Emphasized detailed observations of patients & accurate recordkeeping

7. Thomas Sydenham (cont’)
Volume on gout considered his masterpiece
First to describe scarlet fever (not measles)
Sydenham’s chorea (St. Vitus Dance)
First to use laudanum (tincture of opium) to treat diseases
First to use iron to treat iron deficiency anemia and quinine to treat malaria

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

9. James Lind (cont’) Pioneer of hygiene in the Royal Navy
Proposed the theory that citrus fruits could cure scurvy
Advocate of below-decks ventilation for better health of sailors
Showed that fumigation with arsenic and sulfur worked as a fungicide on ships

10. Edward Jenner ( )
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

11. Ignas Semmelweis (1840’s)
Pioneered hand washing to help prevent the spread of septic infections in mothers following birth 

12. 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

13. John Snow Memorial

14. John Snow’s Cholera Map

15. London- Summer 1858

16. History of Epidemiology (Cont’)
Vital Statistics
John Graunt ( )
William Farr ( )
Occupational medicine
& Industrial Hygiene
Bernardino Ramazzini ( )
Role of carriers in transmission
Typhoid Mary & George Soper

17. 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

18. Typhoid Mary

19. 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)

20. Shattuck Hospital

21. Notable Epidemiology Studies
Framingham Heart Study (1948-present)
Nurses Health Study (1976-present)

22. Notable Epidemiology Studies (cont’)
1954 "The mortality of doctors in relation to their smoking habits. A preliminary report".  
1994 Antiplatelet Trialists' Collaboration. Collaborative overview of randomised trials of antiplatelet therapy--I: Prevention of death, myocardial infarction, and stroke by prolonged antiplatelet therapy in various categories of patients
1989 Cardiac Arrhythmia Suppression Trial (CAST) Investigators. Preliminary report: effect of encainide and flecainide on mortality in a randomized trial of arrhythmia suppression after myocardial infarction.  

23. Notable Epidemiology Stuides (cont’)
1948 MRC Streptomycin in Tuberculosis Trials Committee. Streptomycin treatment of pulmonary tuberculosis.  
1954 Thomas Francis, Robert Korn, et al. "An Evaluation of the Poliomyelitis Vaccine Trials.“  
1994 Randomized trial of cholesterol lowering in 4444 patients with coronary heart disease: The Scandinavian Simvastatin Survival Study  

24. Notable Epidemiology Studies (cont)
1976 Adjuvant study with combination chemotherapy in operable breast cancer.  
1950 Epidemiological Approaches to Heart Disease: The Framingham Study Presented at a Joint Session of the Epidemiology, Health Officers, Medical Care, and Statistics Sections of the American Public Health Association
1855 On the Mode of Communication of Cholera by John Snow, M.D. London: John Churchill, New Burlington Street, England, 1855 

25. Notable Epidemiology Studies (cont’)
A comparison of observational studies and randomized, controlled trials.
Problems of spectrum and bias in evaluating the efficacy of diagnostic tests.
Is the placebo powerless? An analysis of clinical trials comparing placebo with no treatment.
Issues in Comparisons between Meta-analyses and Large Trials.

26. Notable Epidemiology Studies (cont’)
Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial.
[Prevention of the first occurrence of anencephaly and spina bifida with periconceptional multivitamin supplementation (conclusion)]

27. 1964 Surgeon General’s Report on Smoking

28. MASALA Mediators of Atherosclerosis in South Asians Living in America
South Asians (Indian, Pakistani, Bangladeshi, Nepali, and Sri Lankan) have high rates of cardiovascular disease that is not explained by widely known heart disease risk factors such as high blood pressure or smoking.
The MASALA study is trying to identify what factors lead to heart disease in South Asians. The identification of these factors may help us provide information for future treatments to prevent or cure heart disease in South Asians.

29. MESA
The Multi-Ethnic Study of Atherosclerosis a study of the characteristics of subclinical cardiovascular disease (disease detected non-invasively before it has produced clinical signs and symptoms) and the risk factors that predict progression to clinically overt cardiovascular disease or progression of the subclinical disease. MESA researchers study a diverse, population-based sample of 6,814 asymptomatic men and women aged Approximately 38 percent of the recruited participants are white, 28 percent African-American, 22 percent Hispanic, and 12 percent Asian, predominantly of Chinese descent.

30. 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

31. U.S. Gross Mortality Index (annual deaths/100,000)

32. EVOLVING FIELD OF EPIDEMIOLOGY
Chief Causes of Death in the U.S
Pneumonia/Influenza %
Tuberculosis %
Gastritis, enteritis, colitis 8.3%
Heart disease %
Senility, ill-defined conditions 6.8%
Vascular lesions affecting CNS 6.2%
Nephritis and renal sclerosis 4.7%

33. Chief Causes of Death in the U.S. -- 2001*
Disease of heart
Malignant neoplasms
Cerebrovascular diseases 58
Chronic lower respiratory diseases 44
Unintentional injuries
Diabetes mellitus
Pneumonia & influenza
*Age-adjusted per 100,000

34. Wake-up Calls Mayhem……!!! 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
Mayhem……!!!

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

36. Outline History of Epidemiology Basic Concepts and Terminology
Disease Transmission
Morbidity and Mortality

38. The Three Kinds of Lies
“Lies, damn lies and statistics”- Benjamin Disraeli, British Prime Minister (not Mark Twain)

39. DEFINITIONS
What is epidemiology?
What is an epidemiologist?

40. Epi = upon
Demos = people
Ology = science
Epidemiology = the science which deals with what falls upon people…..
Bridge between biomedical, social and behavioral sciences

41. Epidemiology
Study of the occurrence and distribution of health-related diseases or events in specified populations, including the study of the determinants influencing such states, and the application of this knowledge to control the health problem
(Porta M, Last J, Greenland S. A Dictionary of Epidemiology, 2008)

42. The Two 600 lb Gorillas

43. Local Gorillas

44. Epidemiologist
A professional who strives to study and control the factors that influence the occurrence of disease or health-related conditions and events in specified populations and societies, has an experience in population thinking and epidemiologic methods, and is knowledgeable about public health and causal inference in health
(Porta M, Last J, Greenland S. A Dictionary of Epidemiology, 2008)

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

46. What does an Epidemiologist need to know?
Public health: because of the emphasis on disease prevention
•Clinical medicine: because of the emphasis on disease classification and diagnosis  
• Pathophysiology: because of the need to understand basic biological mechanisms in disease
• Biostatistics: because of the need to quantify disease frequency and its relationships to antecedents
• Social sciences: because of the need to understand the social context in which disease occurs and presents

47. Aims of Epidemiologic Research
Describe the health status of a population
To assess the public health importance of diseases
To describe the natural history of disease,
Explain the etiology of disease
Predict the disease occurrence
To evaluate the prevention and control of disease
Control the disease distribution
Descriptive epidemiology Analytic epidemiology Applied epidemiology

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

49. Disease Investigation
Establish diagnosis
Identify specific agent
Describe according to person, place and time
Identify source of agent
Identify mode of transmission
Identify susceptible populations

50. The Epidemiologic Approach
Multistep process
First - determine association
Then prove causation
Not all associations are causal
Examine validity, false assumptions
“The Band Played On”-

51. Epidemiology and Prevention
Identify high risk populations
Modify risks
Prevent exposures

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

53. Endemic: a disease or pathogen present or usually prevalent in a given population or geographic region at all times
Hyperendemic: equally endemic in all age groups of a population
Holoendemic: endemic in most of the children in a population, with the adults in the same population being less often affected
Epidemic: a disease occurring suddenly in numbers far exceeding those attributable to endemic disease; occurring suddenly in numbers clearly in access of normal expectancy
Pandemic: a widespread epidemic distributed or occurring 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

54. Endemic vs. Epidemic Number of Cases of a Disease Epidemic Endemic
Time

55. These term are never to be used interchangeably!!
Incidence: rate of occurrence of an event; number of new cases of disease occurring 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

56. Incubation Period
The period of time after an infection is established but before the first signs or symptoms appear
Different diseases generally have different incubation periods and symptoms
Therefore, can derive epidemic curves

57. Morbidity is another term for illness
Morbidity is another term for illness. A person can have several co-morbidities simultaneously. So, morbidities can range from Alzheimer's disease to cancer to traumatic brain injury. Morbidities are NOT deaths. Prevalence is a measure often used to determine the level of morbidity in a population.

58. Terms Related to Morbidity
The extent of illness, injury or disability in a defined population
Incidence of a disease (Incidence rate)
The number of new cases of a disease that occur during a specified time period (numerator) in a population at risk for developing the disease (denominator)
Prevalence of a disease (Prevalence rate)
The number of total cases of disease present at a particular time (numerator) in a specific population (denominator)
Risk
The likelihood that an individual will contract a disease

59. Mortality is a term which means “death” or describes death and related issues

60. Ro
In epidemiology, the basic reproduction number (sometimes called basic reproductive ratio, or incorrectly basic reproductive rate, and denoted R0, r naught) of an infection can be thought of as the number of cases one case generates on average over the course of its infectious period, in an otherwise uninfected population.[6]
This metric is useful because it helps determine whether or not an infectious disease can spread through a population.

61. Ro
R0 < 1.0 the infection will die out in the long run.
But if
R0 > 1.0 the infection will be able to spread in a population. If
R0 = 1.0 the number of new cases of an infection will remain constant in a population.

62. Ro Diphtheria 6-7 Measles 12-18 Mumps 4-7 Pertussis 12-17 Polio 5-7
Rubella
Smallpox
Norovirus ????

63. Outline History of Epidemiology Basic Concepts and Terminology
Disease Transmission
Mortality

64. Modes of Transmission Contact transmission (direct or indirect)
Vehicle transmission
Vector transmission

70. San Diego 2017 Hep A Epidemic

71. Outline History of Epidemiology Basic Concepts and Terminology
Disease Transmission
Morbidity and Mortality

72. Morbidity and Mortality Weekly Reports
Morbidity and Mortality Weekly Reports

73. Back in the day……

74. Sources of Morbidity Statistics
Clinical and hospital
Managed care
Registries
Vital statistics
Surveys
Disease reporting
Insurance and pre-paid med. care plans
Absenteeism records

76. Three Levels of Mortality Rates
Crude rates
Adjusted rates
Specific rates/ratios

77. Annual Death Rates “General” (crude) mortality rate
a population group exposed to risk of death
a time period
Crude Mortality Rate = # of deaths occurring in that population during that period of time

78. Crude Death Rates
Does NOT account for differences of age, sex, etc. in any aspect of death
Info needed:
total deaths
total population
a given period of time

79. Crude Death Rates

80. Cause Specific Mortality Rate

82. Age-Specific Mortality Rates

83. Remember the last slide for our lecture on influenza!