Infectious Diseases

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Infectious Diseases
2012-03-20 23:38:10

I'm going to binge drink tomorrow
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  1. Epidemioloic Triad
  2. Infectious Disease Agent Factors
    • Ability to live outside of the host
    • Ability to survive unfavorable environments
    • Ability to change antigenicity
  3. Bacteria
    Tuberculosis, pertussis, and anthrax
  4. Viruses
    Measles, influenza, hepatitis B
  5. Fungi
    Coccidiomycosis, histoplasmosis
  6. Protozoa
    Malaria, giardiasis
  7. Helmiths
    Schistosomiasis, trichinosis
  8. Prions
    Cruetzfeldt-Jakob Disease
  9. Agent
    • Infectivity: ability to infect (enter and multiply)
    • Pathogenicity: ability to produce disease
    • Virulence: Ability to produce severe disease
  10. Host Factors
    • Age
    • Genetic Composition
    • Nutritional Status
    • Immunologic Status
    • Behaviors
  11. Immunity
    Passive vs. Active Immunity: natural infection vs. vaccination

    Herd Immunity: resistance of entire population to an infectious agent
  12. Environmental Factors
    • Physical: climate, geology
    • Biologic: insect vectors
    • Socioeconomic: crowdin, sanitation
  13. Epidemiologic Triad-Malaria
    • Host: susceptible traveler
    • Vector: Mosquito
    • Agent: P. Falcinparum
    • Environment: standing water, no bed nets
  14. Reservoir
    Habitat in which an infectious agent normally lives, grows, and multiplies
  15. Human Reservoirs
    • Respiratory Infections: Tuberculosis, Pertussis
    • Sexually-transmitted infecitons: Gonorrhea, Chlamydia
  16. Direct Transmission
    • Direct contact (sexual intercourse, kissing, skin-to skin)
    • Droplet spread (short range aerosols )
  17. Indirect Transmission
    • Common vehicle (food, water)
    • Vector (mosquito, tick)
    • Airborne (suspended air particles)
  18. Vector
    • Living intermediary that conveys the infectious agent from its reservoir to a suscepible host
    • Usually an insect or arthropod (mosquito, tick)
  19. Vehicle
    • NON-LIVING intermediary that conveys the infectious agent from its reservoir to a susceptible host
    • Food, Water, biologic product, fomite (inanimate object)
  20. Incubation Period
    • Time from infection to sympton onset:
    • Heavy metals: minutes
    • Salmonella 12-36 hours
    • HIV months to years
  21. Steps of an Outbreak Investigation
    Eight Very Crazy Farmers Plowed During The Realy Intense Rain

    • Establish the existence of an outbreak
    • Verify the diagnosis
    • Construct a working case definition
    • Findcases systematically
    • Perform descriptive epidemiology
    • Develop Hypotheses
    • Refine hypothesis, if necessary
    • Implement control measures
    • Report, report, report
  22. Epi Curve
    • Shape of an epi curve can tell us the type of outbreak
    • point source
    • continuous common source
    • propagated
  23. Epi Curve- Point Source
    • Persons are exposed to the same exposure over a limited, defined perioud of time
    • Shape of curve commonly rises rapidly and contains a definite peak at the type, followed by a gradual decline
  24. Epi curve- continuous common source
    Exposure to the source is prolonged over an extended period of time
  25. Epi Curve- propagated
    Case serves as a source of infection for subsequent cases
  26. Constructing an Epi Curve
    • Plot the # of disease reported during an outbreak on Y-Axis
    • Plot the date of symptom onset on x-axis
  27. Calculating Attack Rate
    AR= # of people at risk who develop disease / total # people at risk
  28. Attack Rate Ratio
    Attack rate among exposed / attack rate among unexposed
  29. Summary
    • Goal is to break the chain of infection
    • No single right list of outbreak investigation steps
    • Steps are not fixed in order
    • Most components are dynamic