Card Set Information

2013-10-03 13:32:29

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  1. What is epidemiology?
    Essentially the study of transmission and proliferation of disease and its application to control disease
  2. What factors affect the successful transmission of a microorganism
    • 1. Number of microorganisms shed
    • most of shed microorganisms die, with few reaching potential hosts alive ∴ more shedding increases the chance of reaching a fresh host
    • 2. Microorganism stability in the environment
    • thermostability and resistance to drying increase stability (Clostridial endospores, cysts) 
    • decreased stability creates reliance on close contact, vector, or food/water contamination for infection
    • 3. Efficiency of infection (# needed to cause infection)
    • varies between organism (10 Shigella dystenteriae vs 106 Salmonella spp) and route of infection (10 gonococci in urethra vs 1000s gonococci in the oropharynx)
    • 4. Genetic factors in microorganisms: some strains are more readily transmitted than others
    • 5. Utilizing host responses to benefit the microorganism
    • Coughing and sneezing can increase fluid secretions and make transmission more efficient
    • Diarrhea is a highly effective spreading mechanism
  3. How are the most common infections spread?
    • Respiratory/Salivary
    • Fecal-Oral
    • Venereal
  4. How is humidity related to transmission from the respiratory tract?
    • Ill-ventilated rooms are more humid, favoring survival of suspended microorganisms
    • Air-conditioned rooms tend to be dry which impair mucociliary activity
  5. What are the VERY BASIC 3 steps in fecal-oral spread
    • Poor public health and hygiene
    • Fecal microbes appear in water and food
    • Susceptible individuals are infected
  6. What are the two methods of venereal transmission w/ organisms and description?
    • Purulent (pus-like) discharge: N. gonorrhoeae, Chlamydia trachomatis
    • induce discharge to carry organisms over epithelial surfaces easily for transmission
    • Mucosal sores (ulcers): herpes simplex virus
    • cold sores are sites that contain virus particles
  7. What are the social factors that facilitate STDs?
    • An increased number of sexual partners per person
    • Decline of belief that sexual activity is sinful
    • Knowledge that STDs are treatable and pregnancy is avoidable
    • ***favor of the pill over mechanical barriers for contraception
  8. What are examples of infectious agents of the oropharynx?
    • streptococci and tubercle bacilli reach saliva during respiratory tract infections
    • paramyxovirus, herpes simplex virus, cytomegalovirus, and human herpesvirus type 6  infect the salivary glands
  9. What are the two methods of transmission from the skin?  Which is more common? Example microorganisms?
    • Direct contact/contaminated fingers is much more common than release into environment
    • Can include staphylococci and human papillomaviruses
  10. What organisms can be shed in human milk?
    HIV, cytomegalovirus (CMV), human T-cell lymphotropic virus (HTLV1)
  11. What are the two main paths for transmission from blood?
    • Blood-sucking arthropods
    • Needles (transfusion, drug use, etc)
  12. What is vertical transmission? Horizontal? Importance of each?
    • Vertical transmission: from parents to offspring via sperm, ovum, placenta, milk, or blood
    • Only important in small, isolated, communities since there are only a few affected individuals per lifecycle
    • Horizontal transmission: from individual to individual
    • Cause quick spread amongst populations
  13. What are the most important vectors?  Examples of devastating diseases caused by vectors w/ organism.
    • Insects, ticks, and mites (the bloodsuckers)
    • Yersiania pestis spread by fleas of rats caused the plague
    • Rickettsia typhi, Rickettsia prowazekii spread by lice caused typhus
    • Plasmodium spread by Anopheles mosquito causes malaria
  14. Aquatic molluscs are necessary intermediate hosts for....?
    Schistosomes (blood flukes)
  15. Describe the major infections from domestic pets
    • Toxocariasis: (from dogs) caused by roundworms (Toxocara canis) that can be transmitted from dogs OR cats.  Can cause blindness and rheumatic, neurologic, or asthmatic symptoms
    • Toxoplasmosis: (from cats) caused by protozoan Toxoplasma gondii which affects brain, lung, heart, eyes, or liver