Overview
• Introduction to Public Health• What is Epidemiology?
History Who Uses It?
• Terminology• Infectious Disease Transmission• The Host Community• Disease Burden
Introduction to Pubic Health
What is it? A field devoted to the promotion and
maintenance of well-being
Attributes Multidisciplinary Often focused on prevention rather than
treatment (upstream) Operates on multiple levels
What is Epidemiology?
Two Definitions:• “The study of the occurrence, distribution,
and determinants of health and disease in a population”
• “The study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems”
History of Epidemiology• Almost 400 years old!• “First” epidemiologist:
John Graunt• William Farr• Controlled trials! (public
health people love these)• Shift from studying
infectious to chronic diseases
• Divergence: molecular and genetic epidemiology vs. social epidemiology
Who Uses Epidemiology?
• Health Care Service Providers• Governments
Legislature Health Departments
• International Health & Development Agencies• Community-based NGOs• Researchers• Journalists• You
Terminology (cont’d)
• Case An instance of a disease or health condition in an
individual• Incidence
Number of new cases of a disease or health condition in a population over a given period of time
• Prevalence Number of new and existing cases of a disease or
health condition in a population over a given time period
What’s are the incidence and prevalence for the class?• Incidence = _____ /
~70 (per hour)
• Prevalence = ___ +___ /~70 (per hour
Symptoms of Glitter Disease
Terminology (cont’d)
• Morbidity Used commonly to mean illness Morbidity Rate: refers to the incidence of disease in a
population• Mortality
Used commonly to mean death Mortality Rate: refers to the incidence of death in a
population➡Morbidity from a disease can be high without
mortality being high
Terminology (cont’d)
• Host – organism capable of supporting the growth of a virus or other parasite
• Carrier – sub-clinically infected individuals who may spread a disease Examples?
Terminology (cont’d)
• Reservoir – source of viable infectious agents from which individuals may be infected Vector – agent (usually insect or animal) able to
carry pathogens from one host to another Vehicle – nonliving source of pathogens that infect
large numbers of individuals (food, water, etc)
Terminology (cont’d)
• Zoonosis – a disease, primarily of animals, that is occasionally transmitted to humans Examples: avian and swine flu
Don’t forget to cover your snout when you sneeze!
Terminology (cont’d)
Disease Progression• Infection• Incubation Period• Acute Period• Decline Period• Convalescent Period
Direct Host-to-Host Transmission
• Pathogen transmitted directly from host to host Respiratory illnesses Sexually-transmitted
infections Skin infections
Vampirism?
Indirect Host-to-Host Transmission
• Transmitted through living agents (vectors) or inanimate agents (vehicles)
Mosquito: vector Lenoir food: vehicle
Epidemics
Common-source epidemic• Transmission can occur
rapidly• Classic example: London’s
cholera epidemic in the 1850’s
Epidemics (cont’d)
Host-to-Host Epidemic• Typically occurs over a longer period of time
than the common-source epidemic• Examples: Influenza, Chickenpox
Coevolution
• The continued existence of host and pathogen frequently requires coevolution
• Examples Myxoma Malaria E. coli
Herd Immunity (cont’d)
• Resistance of a group to infection due to the immunity of a high proportion of individuals
• Depends on: Density of thepopulation Virulence of theagent
The Host Community
• Disease is not purely biological!• Behavior matters
Examples of protective behaviors?
• Who you are matters Racism sexism classism Etc.
Sources• Aschengrau A, Seage G. Essentials of Epidemiology in Public Health. 2nd Ed. Jones and Bartlett
Publishers, Inc. Salsbury, MA, 2008.• Clark DP, Dunlap PV, Madigan MT, Marinko MM. Brock Biology of Microorganisms. 12th Ed. Pearson
Edu, Inc. San Fransisco, CA, 2009.• http://a3.vox.com/6a00c2252582c1f21900d4144dabbb6a47-500pi• http://himetop.wdfiles.com/local--files/broad-street-pump/Broad%20Street%20Pump.jpg• http://mydogumentary.files.wordpress.com/2009/08/mosquito.jpg• http://farm4.static.flickr.com/3123/2604408184_5718abdaa8.jpg• http://www.independent.co.uk/multimedia/archive/00079/twilight_79981t.jpg• http://images.buyfairycostumes.com/deluxe-fairy-makeup.jpg• http://www.measlesinitiative.org/mi/photos• http://www.whspip.co.uk/images/occu2.jpg• http://www.msf.ca/blogs/cholera/files/2009/03/latrine.jpg• http://www.youtube.com/watch?v=6Pq98sZSBtc• http://www.medicine.manchester.ac.uk/images/epidemiology/home_checkerboard.jpg• http://www.youtube.com/watch?v=LU8DDYz68kM• http://www.dailytarheel.com/content/fewer-h1n1-cases-reported