Bmsc210 Final p5

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  1. Epidemiology
    (3 categories of study)
    – The study of the occurrence, distribution, and determinants of health and disease in a population
  2. In developed countries infectious diseases cause ___ deaths than noninfectious diseases
  3. Worldwide, infectious disease accounts for __% of all deaths
  4. Infectious disease hit an all time low around 19__
  5. Chronic infections:
    • -host and pathogen survive
    • -New pathogens sometimes emerge for which the host has no resistance
  6. Acute infections:
    pathogen eithers kills or is killed not chronic
  7. Epidemiologists trace the spread of disease to identify its ___ and mode of ___
    • origin
    • transmission
  8. A disease is an ___ when it occurs in a large number of people in a population at the same time
  9. A ___ is widespread, usually worldwide
  10. An ___ disease is constantly present in a population, usually at low incidences
  11. The ___ of a disease is the number of newcases of the disease in a given period of time
  12. The ___ of a disease is the total number of new and existing cases in a population in a given time
  13. arrange diseases according to prevalance
    endemic < epidemic < pandemic
  14. subclinical infections
    • -Diseased individuals who show no or mild symptoms
    • -Subclinical individuals are called carriers
  15. Mortality
    is the incidence of death in a population
  16. Morbidity
    -incidence of disease including fatal and nonfatal diseases (all)
  17. Infection:
    the organism invades and colonizes the host
  18. Incubation period:
    the time between infection and onset of symptoms
  19. Acute period:
    the disease is at its height
  20. Decline period:
    disease symptoms are subsiding
  21. Convalescent period:
    patient regains strength and returns to normal
  22. Reservoirs
    • -sites in which infectious agents remain viable and from which infection of individuals can occur
    • –humans, animals and nonliving matter can all serve as reservoirs
    • • For example, soil is a reservoir for Clostridiumtetani, the cause of tetanus
  23. Zoonosis
    • -any disease that primarily infects animals, but is occasionally transmitted to humans
    • – Control of a zoonotic disease in the human population may not eliminate the disease as a potential public health problem
    • – Certain infectious diseases have complex lifecycles involving an obligate transfer from a nonhuman host to humans followed by transfer back to the nonhuman host
  24. Carriers
    • – Pathogen-infected individuals showing no signsof clinical disease, i.e. Typhoid Mary
    • – Potential sources of infections
    • – May be individuals in the incubation period of the disease
    • – Can be identified using diagnostic techniques, including culture and immunoassays
  25. Epidemiologists follow transmission of a disease by correlating:
    (4 types of data)
    • geographic
    • climatic
    • social
    • and demographic data
  26. Direct host-to-host transmission
    – Infected individual transmits a disease directly to a susceptible host without the assistance of an intermediary (e.g., flu, common cold, STDs,ringworm)
  27. Indirect host-to-host transmission
    – Occurs when transmission is facilitated by a living or nonliving agent
  28. vectors
    Living transmission agents
  29. fomites
    Nonliving transmission agents
  30. A common-source epidemic
    • usually arises from contamination of water or food
    • • Example: cholera
    • -spike quickly and die off quickly
  31. host-to-host epidemic
    • the disease shows a slow, progressive rise and a gradual decline
    • • Example: influenza and chicken pox
  32. why is coevolution of a host and its parasite common?
    • Virulence of the parasite in host-to-host transmission diminishes and resistance of the host increases
    • (e.g., myxoma virus introduced to control rabbits in Australia)
    • • A host-to-host pathogen that kills its host before it can infect another host may become extinct
    • -as the grow together virulence and mortality should drop to optimum levels
  33. Herd immunity
    -the resistance of a group to infection due to immunity of a high proportion of the group
  34. How does Herd immunity work?
    • – If a high proportion of individuals are immune to an infection then the whole population will be protected
    • – Immunized people protect nonimmunized people because the pathogen cannot be passed on and the cycle of infectivity is broken
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Bmsc210 Final p5
2013-04-22 00:26:05
Bmsc210 Final p5

Bmsc210 Final p5
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