1. Ch Epidemiology
Microbiology

2. 10.1 History of Epidemiology
Epidemiology is the study of patterns, causes, and effects of health and disease conditions in defined populations.
Identifies risk factors and provides targets for preventative medicine.
Developed methodology used in clinical research and public health studies.
Greek physician Hippocrates was first recorded epidemiologist.
Epidemic-”visited upon”
Endemic-”reside within”
Syndemic-interaction of diseases

3. 10.1 History of Epidemiology
1858 Dr. John Snow, father of modern epidemiology, identified cause and solution to cholera outbreak in London using maps to identify source of contamination.
1954 Mathematical methods were introduced which showed the statistical relationship between lung cancer and smoking.

4. 10.1 The Science of Epidemiology
Disease etiology
Observational
Experimental
Disease surveillance
Disease screening
Biomonitoring
Clinical Trials
Randomized control
Field trials
Community trials

5. 10.1 Vocabulary of Epidemiology
Outbreak-greater occurrence than expected.
Asymptomatic-”carrier”, has no symptoms.
Pandemic-disease spread worldwide.
Incidence-risk of disease over a period of time.
Prevalence-total number of cases in a population.
Morbidity-diseased state.
Mortality-death rate.
Progression: infection, incubation, acute, decline & convalescent periods.

6. 10.1 Koch’s Postulates
Four criteria designed in the 1880’s to establish a causal relationship between microbe and disease.
Microorganism must be found in abundance in all diseased organisms.
Microorganism must be isolated and grown in culture.
The cultured microorganism should cause disease when introduced to a healthy organism.
The microorganism must be reisolated and shown to be identical to original.

7. 10.1 Exceptions to Koch’s Postulates
First postulate abandoned after the discovery of asymptomatic carriers of cholera.
The second postulate may be suspend for certain microorganisms that cannot be grown in culture such as prions.
The third postulate specifies “should” not “must” because as Koch proved himself not all organisms exposed to the infectious agent will acquire the infection such as in the cases of tuberculosis and cholera.

8. 10.2 Occurrence of a Disease
Outbreaks
Verify the diagnosis
Identify the existence
Create a case definition
Map the spread
Develop a hypothesis
Study hypothesis
Refine hypothesis
Develop and implement control and prevention systems
Release findings

9. 10.2 Occurrence of a Disease
Outbreak Patterns
Common source
Continuous source-multiple incubation periods
Point source-less than one incubation period
Propagated-person to person
Other Factors
Behavioral risk related- STD’s
Zoonotic-vectors

10. 10.2 Disease Severity & Duration
World Health Organization (WHO)
Scope of disease
Localized-only part of the body
Disseminated-spread to other parts of the body
Systemic-affects the entire body

11. 10.2 Disease Severity & Duration
International Classification of Diseases (ICD)
Acute-short-lived
Chronic-long period of time (6 months min.)
Flare-up-recurrence
Refractory-resists treatment
Progressive-gets worse over time
Remission-symptoms stop or lessen for a period of time
Cure-complete remission

12. 10.2 Extent of Host Involvement
Primary pathogens-cause disease as a result of their presence or activity within the normal healthy host.
Intrinsic virulence-need to reproduce and spread
Opportunistic pathogens- cause infections in a host with depressed resistance.
Genetic defects
Exposure to antimicrobial drugs or immunosuppressive chemicals
Exposure to radiation

13. 10.2 Identification of Microbes Based on Molecular Genetics
Genome-genetic sequence ID
Very sensitive
Revised Koch’s postulates
Nucleic acid sequence present
Fewer, or not present in healthy individuals
Decrease with resolution
Sequence copy number correlates with severity
Known biological characteristics
Tissue-sequence correlation
Reproducible
Vaccine development
Not yet possible for many pathogenic organisms