Lec_2_Exposure - ExposureRoutes/ Infectious Disease...

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Unformatted text preview: ExposureRoutes/ Infectious Disease Epidemiology ENV H 451/541c John Scott Meschke Office: Suite 2338, 4225 Roosevelt Phone: 206-221-5470 Email: jmeschke@u.washington.edu Todays Objectives 1. Recognize the various routes of exposure and portals of Entry/Exit 2. Become familiar with terminology of infectious disease epidemiology 3. Learn to calculate incidence and prevalence 4. Recognize a common source outbreak 5. Learn types, progression, and outcomes of infection FACTORS INFLUENCING EXPOSURE AND INFECTION: Agent Factors Sources, Reservoirs, Transport and Persistence (in the Environment) Ability to Enter a Portal in the Human or Other Host Ability to Reach and Proliferate at Site(s) of Infection in the Host Excretion of the Agent from the Host Quantity and "Quality" (including virulence) of the Infectious Factors Influencing Exposure and Infection: Environmental Factors Reservoirs : where organisms can live, accumulate or persist outside of the host of interest; could be another organism or the inanimate environment. Vehicles : inanimate objects/materials by which organisms get from one host to another; includes water, food, objects (called fomites) and biological products (e.g., blood). Amplifiers : Types of reservoirs where organisms proliferate; often applied to organisms transmitted by the airborne route. Factors Influencing Exposure and Infection: Environmental Factors Vectors : Living organisms bringing infectious organisms to a host. Mechanical vectors: Microbes do not multiply in the vector ex: biting insects infected with the infectious organism Biological vectors: Microbes must propagate in the vector before they can be transmitted to a host. Environmental Factors Influencing Survival or Proliferation of Infectious Agents Physical : temperature, relative humidity, sunlight, moisture content or water activity, climate and weather, etc. Chemical and Nutritional : Antimicrobial chemicals, nutrients for microbial proliferation. Biological : Antagonistic activity by other organisms: antimicrobial agents, parasitism, etc.; presence and state of a vector Factors Influencing Exposure and Infection: Host Factors and Host Susceptibility Opportunities for host exposure transmission routes host availability Susceptibility factors Dosage (quantity) and "quality" of infectious organisms, including their "virulence"; age immunity nutritional status immunocompetence and health status, genetics behavior (personal habits) of host. Routes of Transmission Direct Personal Contact: Person (animal)-to-Person Indirect Personal Contact: Droplet, Fomites, Other Vehicles Water and Food (Gastrointestinal Tract) Vector-borne: often insects Intrauterine or Transplacental Organ Transplants, Blood and Blood Products Sites or Portals of Entry to and/or Exit From the Body Respiratory Enteric or Gastrointesti nal Skin: especially if skin barrier is penetrated Genitourinar y Eye Possible Outcomes of Exposure...
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Lec_2_Exposure - ExposureRoutes/ Infectious Disease...

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